Methods for treatment of sleep apnea

ABSTRACT

A method for delivering energy as a function of degree coupling may utilize an external unit configured for location external to a body of a subject and at least one processor associated with the implant unit and configured for electrical communication with a power source. The method may determine a degree of coupling between the primary antenna and a secondary antenna associated with the implant unit, and regulate delivery of power to the implant unit based on the degree of coupling between the primary antenna and the secondary antenna.

RELATED APPLICATIONS

This application is a continuation-in-part application of applicationSer. No. 13/629,690, filed on Sep. 28, 2012, application Ser. No.13/629,694, filed on Sep. 28, 2012, application Ser. No. 13/629,701,filed on Sep. 28, 2012, application Ser. No. 13/629,712, filed on Sep.28, 2012, application Ser. No. 13/629,725, filed on Sep. 28, 2012,application Ser. No. 13/629,730, filed on Sep. 28, 2012, applicationSer. No. 13/629,741, filed on Sep. 28, 2012, application Ser. No.13/629,741, filed on Sep. 28, 2012, application Ser. No. 13/629,748,filed on Sep. 28, 2012, application Ser. No. 13/629,748, filed on Sep.28, 2012, application Ser. No. 13/629,757, filed on Sep. 28, 2012,application Ser. No. 13/629,762, filed on Sep. 28, 2012, applicationSer. No. 13/629,793, filed on Sep. 28, 2012, application Ser. No.13/629,819, filed on Sep. 28, 2012, application Ser. No. 13/630,392,filed on Sep. 28, 2012, application Ser. No. 13/629,721, filed on Sep.28, 2012, and application Ser. No. 13/629,686, filed on Sep. 28, 2012,each of which claims the benefit of priority under 35 U.S.C. §119(e) toU.S. Provisional Application No. 61/541,651, filed Sep. 30, 2011, andalso to U.S. Provisional Application No. 61/657,424, filed Jun. 8, 2012.Additionally, application Ser. Nos. 13/629,686, and 13/629,721, are alsocontinuations-in-part of both application Ser. No. 12/642,866, filedDec. 21, 2009, and of application Ser. No. 12/581,907, filed Oct. 20,2009. All of the above referenced applications are incorporated hereinby reference in their entirety.

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to devices andmethods establishing communications between an implantable device and anexternal unit. In some cases, the implantable unit may be configured formodulating a nerve. More particularly, embodiments of the presentdisclosure relate to devices and methods for modulating a nerve throughthe delivery of energy via an implantable electrical modulator.

BACKGROUND

Neural modulation presents the opportunity to treat many physiologicalconditions and disorders by interacting with the body's own naturalneural processes. Neural modulation includes inhibition (e.g. blockage),stimulation, modification, regulation, or therapeutic alteration ofactivity, electrical or chemical, in the central, peripheral, orautonomic nervous system. By modulating the activity of the nervoussystem, for example through the stimulation of nerves or the blockage ofnerve signals, several different goals may be achieved. Motor neuronsmay be stimulated at appropriate times to cause muscle contractions.Sensory neurons may be blocked, for instance to relieve pain, orstimulated, for instance to provide a signal to a subject. In otherexamples, modulation of the autonomic nervous system may be used toadjust various involuntary physiological parameters, such as heart rateand blood pressure. Neural modulation may provide the opportunity totreat several diseases or physiological conditions, a few examples ofwhich are described in detail below.

Among the conditions to which neural modulation may be applied isobstructive sleep apnea (OSA). OSA is a respiratory disordercharacterized by recurrent episodes of partial or complete obstructionof the upper airway during sleep. During the sleep of a person withoutOSA, the pharyngeal muscles relax during sleep and gradually collapse,narrowing the airway. The airway narrowing limits the effectiveness ofthe sleeper's breathing, causing a rise in CO₂ levels in the blood. Theincrease in CO₂ results in the pharyngeal muscles contracting to openthe airway to restore proper breathing. The largest of the pharyngealmuscles responsible for upper airway dilation is the genioglossusmuscle, which is one of several different muscles in the tongue. Thegenioglossus muscle is responsible for forward tongue movement and thestiffening of the anterior pharyngeal wall. In patients with OSA, theneuromuscular activity of the genioglossus muscle is decreased comparedto normal individuals, accounting for insufficient response andcontraction to open the airway as compared to a normal individual. Thislack of response contributes to a partial or total airway obstruction,which significantly limits the effectiveness of the sleeper's breathing.In OSA patients, there are often several airway obstruction eventsduring the night. Because of the obstruction, there is a gradualdecrease of oxygen levels in the blood (hypoxemia). Hypoxemia leads tonight time arousals, which may be registered by EEG, showing that thebrain awakes from any stage of sleep to a short arousal. During thearousal, there is a conscious breath or gasp, which resolves the airwayobstruction. An increase in sympathetic tone activity rate through therelease of hormones such as epinephrine and noradrenaline also oftenoccurs as a response to hypoxemia. As a result of the increase insympathetic tone, the heart enlarges in an attempt to pump more bloodand increase the blood pressure and heart rate, further arousing thepatient. After the resolution of the apnea event, as the patient returnsto sleep, the airway collapses again, leading to further arousals.

These repeated arousals, combined with repeated hypoxemia, leaves thepatient sleep deprived, which leads to daytime somnolence and worsenscognitive function. This cycle can repeat itself up to hundreds of timesper night in severe patients. Thus, the repeated fluctuations in andsympathetic tone and episodes of elevated blood pressure during thenight evolve to high blood pressure through the entire day.Subsequently, high blood pressure and increased heart rate may causeother diseases.

Efforts for treating OSA include Continuous Positive Airway Pressure(CPAP) treatment, which requires the patient to wear a mask throughwhich air is blown into the nostrils to keep the airway open. Othertreatment options include the implantation of rigid inserts in the softpalate to provide structural support, tracheotomies, or tissue ablation.

Another condition to which neural modulation may be applied is theoccurrence of migraine headaches. Pain sensation in the head istransmitted to the brain via the occipital nerve, specifically thegreater occipital nerve, and the trigeminal nerve. When a subjectexperiences head pain, such as during a migraine headache, theinhibition of these nerves may serve to decrease or eliminate thesensation of pain.

Neural modulation may also be applied to hypertension. Blood pressure inthe body is controlled via multiple feedback mechanisms. For example,baroreceptors in the carotid body in the carotid artery are sensitive toblood pressure changes within the carotid artery. The baroreceptorsgenerate signals that are conducted to the brain via theglossopharyngeal nerve when blood pressure rises, signaling the brain toactivate the body's regulation system to lower blood pressure, e.g.through changes to heart rate, and vasodilation/vasoconstriction.Conversely, parasympathetic nerve fibers on and around the renalarteries generate signals that are carried to the kidneys to initiateactions, such as salt retention and the release of angiotensin, whichraise blood pressure. Modulating these nerves may provide the ability toexert some external control over blood pressure.

At least some of the presently disclosed embodiments may include methodsof communicating between an implantable device, such as a neuralmodulator, and an external unit configured to communicate with theimplantable device. In applications related to nerve modulation, suchmethods of communication may increase the efficiency of signaltransmission between the implantable device and the external unit. Suchmethods of communication may also assist in other applications; forexample, where an implantable device may include a sensor to sense oneor more physiological conditions. For example, an implantable glucosesensor may monitor glucose levels of a subject, and, utilizingcommunication methods disclosed herein, relay information about glucoselevels to an external device.

The foregoing are just a few examples of conditions to whichneuromodulation may be of benefit, however embodiments of the inventiondescribed hereafter are not necessarily limited to treating only theabove-described conditions.

SUMMARY

A device according to some embodiments may include a housing configuredfor temporary affixation on at least one of a neck and a head of asubject. The device may also include at least one processor associatedwith the housing and configured for electrical communication with apower source, and an antenna associated with the at least one processor.The at least one processor may be configured to communicate with animplant circuit in at least one of the neck and the head of the subjectin a location proximate a hypoglossal nerve, cause the implant circuitto receive power in a first power mode and in a second power mode,wherein a first level of power delivered in the first power mode is lessthan a second level of power delivered in the second power mode, andwherein during a therapy period, power delivery in the first mode occursover a total time that is greater than about 50% of the therapy period.

A device according to some embodiments may include a housing configuredfor location external to a body of a subject. The device may alsoinclude at least one processor associated with the housing andconfigured for electrical communication with a power source, and anantenna associated with the at least one processor. The at least oneprocessor may be configured to communicate with an implant circuitlocated within the body of the subject, cause the implant circuit toreceive power in a first power mode and in a second power mode, whereina first level of power delivered in the first power mode is less than asecond level of power delivered in the second power mode, and whereinduring a therapy period, power delivery in the first mode occurs over atotal time that is greater than about 50% of the therapy period.

A device according to some embodiments may include a primary antenna anda housing configured for location external to a body of a subject. Thedevice may also include at least one processor associated with thehousing and the primary antenna and configured for electricalcommunication with a power source. The at least one processor may befurther configured to communicate with an implant circuit implanted in ablood vessel of the subject proximate to at least one of a renal nerve,a baroreceptor, and a glossopharyngeal nerve of the subject, cause theimplant circuit to receive power in a first power mode and in a secondpower mode, wherein a first level of power delivered in the first powermode is less than a second level of power delivered in the second powermode, and wherein during a therapy period, power delivery in the firstmode occurs over a total time that is greater than about 50% of thetherapy period.

A device according to some embodiments may include a patch configuredfor placement on a side of a hairline opposite a substantially hairedregion of a head of a subject. The device may also include at least oneprocessor associated with the patch and configured for electricalcommunication with a power source, and a primary antenna associated withthe at least one processor. The at least one processor may be configuredto communicate, via the primary antenna, with a secondary antennalocated beneath the skin of a subject on a side of a hairline opposite asubstantially haired region of the subject, cause an implant circuit toreceive power through the secondary antenna in a first power mode and ina second power mode, wherein a first level of power delivered in thefirst power mode is less than a second level of power delivered in thesecond power mode, and wherein during a therapy period, power deliveryin the first mode occurs over a total time that is greater than about50% of the therapy period.

Some embodiments may include a method of delivering power to animplanted circuit. The method may include communicating with theimplanted circuit, which is implanted in a body of a subject. The methodmay also include transmitting power to the implanted circuit in a firstpower mode and in a second power mode, wherein a first level of powerdelivered in the first power mode is less than a second level of powerdelivered in the second power mode, and wherein during a therapy period,power delivery in the first power mode occurs over a total time that isgreater than about 50% of the therapy period.

A device according to some embodiments may include a housing configuredfor location external to a body of a subject. The device may alsoinclude at least one processor associated with the housing andconfigured to communicate with a circuit implanted in the subject withinproximity to a tongue of the subject, wherein the circuit is inelectrical communication with at least one electrode, receive aphysiological signal from the subject via the circuit, and send acontrol signal to the implanted circuit in response to the physiologicalsignal, wherein the control signal is predetermined to activateneuromuscular tissue within the tongue.

Some embodiments may include a method of activating neuromuscular tissuewithin an implanted circuit. The method may include communicating withthe implanted circuit, which is implanted within a proximity of a tongueof a subject, wherein the implanted circuit is in electricalcommunication with at least one electrode, receiving a physiologicalsignal from the subject via the implanted circuit, sending a controlsignal to the implanted circuit in response to the physiological signal,and activating neuromuscular tissue within the tongue of the subject viathe control signal.

A device according to some embodiments may include a housing configuredfor location external to a body of a subject. The device may alsoinclude at least one processor associated with the housing andconfigured to communicate with a circuit implanted in a blood vessel ofthe subject within proximity to at least one of a renal nerve, abaroreceptor, and a glossopharyngeal nerve, wherein the circuit is inelectrical communication with at least one electrode, receive aphysiological signal from the subject, and send a control signal to theimplanted circuit in response to the physiological signal, wherein thecontrol signal is predetermined to modulate nerve tissue to affect bloodpressure.

A device according to some embodiments may include a housing configuredfor location external to a body of a subject. The device may alsoinclude at least one processor associated with the housing andconfigured to communicate with a circuit implanted in the subject withinproximity to at least one nerve to be modulated, wherein the circuit isin electrical communication with at least one electrode, receive aphysiological signal from the subject, and send a control signal to theimplanted circuit in response to the physiological signal, wherein thecontrol signal is predetermined to modulate the at least one nerve to bemodulated.

A device according to some disclosed embodiments may include an externalunit configured for location on a neck of a subject to communicate withan Implant unit implanted proximal to a tongue of a subject. Anindicator, associated with the external unit, may be configured toproduce an indicator signal when the external unit is within apredetermined range of the implant unit. In addition, the indicator maybe configured to vary the indicator signal according to a distancebetween the external unit and the implant unit.

A device according to some disclosed embodiments may include an externalunit configured to communicate with an implant unit beneath the skin ofa subject, an indicator associated with the external unit, and at leastone processor configured to generate a primary signal on a primaryantenna associated with the external unit. The primary signal beingconfigured to cause a secondary signal on a secondary antenna associatedwith the implant unit. In addition, the processor may be configured todetermine a degree of coupling between a primary antenna associated withthe external unit and a secondary antenna associated with the implantunit and cause the indicator to produce a signal when the degree ofcoupling exceeds a predetermined threshold.

A device according to some disclosed embodiments may include an externalunit configured to communicate with an implant unit beneath the skin ofa subject and an indicator associated with the external unit. Theindicator being configured to produce an indicator signal when theexternal unit is within a predetermined range of the implant unit andbeing configured to vary the indicator signal according to a distancebetween the external unit and the implant unit.

A device according to some disclosed embodiments may include a housing,configured for location on a subject to communicate with an implant unitimplanted proximate to at least one of a renal nerve, a baroreceptor,and a glossopharyngeal nerve, and an indicator associated with thehousing. The indicator may be configured to produce an indicator signalwhen the housing is within a predetermined range of the implant unit. Inaddition, the indicator may be configured to vary the indicator signalaccording to a distance between the housing and the implant unit.

A device according to some disclosed embodiments may include a patchconfigured for placement on a side of hairline opposite a substantiallyhaired region of a subject and an indicator associated with the patch.The indicator may be configured to produce an indicator signal when thepatch is within a predetermined range of the implant unit. In addition,the indicator may be configured to vary the indicator signal accordingto a distance between the patch and the implant unit.

The device may further include one or more of the following features:the indicator signal may include a visual output, a tactile output, anaudible output, or an electrical signal configured to communicate withthe implant unit; the electrical signal may cause the implant unit tomodulate a nerve and to induce at least one of a proprioceptive orkinesthesic reaction in the subject; the external unit may comprise atleast one processor; the at least one processor being configured to:generate a primary signal on a primary antenna associated with theexternal unit, the primary signal being configured to cause a secondarysignal on a secondary antenna associated with the implant unit;determine a degree of coupling between the primary antenna associatedwith the external unit and the secondary antenna associated with theimplant unit; and cause the indicator to produce the indicator signalwhen the degree of coupling exceeds a predetermined threshold;determination of the degree of coupling between the primary antennaassociated with the external unit and the secondary antenna associatedwith the implant unit may be based, at least in part, on a measure ofcapacitive coupling, on a measure of radio frequency coupling, on ameasure of inductive coupling, or on an observation of non-linearbehavior in a circuit associated with the implant unit; the observationof non-linear behavior may include at least one of observation of atransition from linear behavior to non-linear behavior or observation ofnon-linear harmonic behavior.

In addition, the processor may further be configured to cause theindicator to produce the indicator signal when the degree of couplingdoes not exceed a predetermined threshold; the at least one processormay be configured to operate in a placement mode and a therapy mode,cause the indicator to produce the variable signal during operation inthe placement mode, and transition from the placement mode to thetherapy mode when a correct placement condition is satisfied; thecorrect placement condition may include at least one of a predeterminedcoupling threshold and a predetermined timing threshold, such that thepredetermined timing threshold includes a pre-sleep waiting period. Thedevice may further comprise a skin patch with an adhesive and configuredfor adherence to the skin of the subject, such that the external unit isremovably connected to the skin patch, and such that the at least oneprocessor is configured to operate in a placement mode when the externalunit is connected to the skin patch.

A method of locating an external unit with respect to an implant unitaccording to some disclosed embodiments may include the steps ofdetecting a distance between the external unit and the implanted unitlocated beneath the skin of a subject, producing an indicator signalwhen the external unit is within a predetermined range of the implantunit, and varying the indicator signal as a function of a distancebetween the external unit and the implant unit.

A device according to some disclosed embodiments may include an externalunit comprising at least one processor. The processor may be configuredto receive a signal indicative of tongue movement in a subject from animplant unit implanted in the subject, determine whether the tonguemovement is representative of sleep disordered breathing, generate amodulation control signal to correct the sleep disordered breathing whenthe at least one processor determines an occurrence of sleep disorderedbreathing.

The device may further include one or more of the following features:the at least one processor may be configured to determine whether thesleep disordered breathing includes an apnea precursor, determinewhether the sleep disordered breathing includes hypopnea, and/ordetermine whether the sleep disordered breathing includes an hypopneaprecursor; the implant unit may be implanted in a location in contactwith the subject's tongue muscle; and there may be a primary antenna inelectrical communication with the at least one processor, the primaryantenna being configured to transmit the modulation control signal to asecondary antenna associated with the implant unit, such that themodulation control signal includes a stimulation control signalconfigured to interact with the implant unit to cause a contraction ofthe muscle.

In addition, the signal indicative of tongue movement may be indicativeof relative motion between a primary antenna associated with the atleast one processor and a secondary antenna associated with the implantunit; the at least one processor may be further configured to generate asub-modulation control signal for transmission to the implant unit viathe primary antenna and/or detect relative motion between the primaryantenna and the secondary antenna based on a degree of coupling betweenthe primary antenna and the secondary antenna; the degree of couplingmay include at least one of a measure of capacitive coupling,radiofrequency coupling, or inductive coupling; the degree of couplingmay further include a measure of non-linear behavior in a circuitassociated with the implant unit; and the at least one processor may beconfigured to adjust at least one characteristic of the modulationcontrol signal based on a severity of the sleep disordered breathing,the at least one characteristic of the modulation control signalincluding voltage amplitude, current amplitude, pulse frequency, orpulse duration.

Another device according to some disclosed embodiments may include anexternal unit comprising at least one processor. The at least oneprocessor may be configured to receive a signal indicative of movementof a subject's tongue, generate a modulation control signal based on thereceived signal indicative of movement of the subject's tongue, andtransmit the modulation control signal via a primary antenna to asecondary antenna associated with an implant unit.

The device may further include one or more of the following features:the modulation control signal may include a stimulation control signalconfigured to interact with the implant unit to cause a contraction in amuscle, the signal may be indicative of movement of a subject's tongueis indicative of relative motion between the primary antenna and thesecondary antenna associated with the implant unit; the at least oneprocessor may further be configured to generate a sub-modulation controlsignal for transmission to the implant unit via the primary antenna, anddetect relative motion between the primary antenna and the secondaryantenna based on a determination of a degree of coupling between theprimary antenna and the secondary antenna; the determination of thedegree of coupling may include at least one of a measure of capacitivecoupling, radiofrequency coupling, inductive coupling, or an observationof non-linear behavior in a circuit associated with the implant unit;and the at least one processor may further be configured to adjust atleast one characteristic of the modulation control signal based on themovement of the subject's tongue, the at least one characteristic of themodulation control signal including voltage amplitude, currentamplitude, pulse frequency, or pulse duration.

A method for detecting tongue movement in a subject according to somedisclosed embodiments may include receiving from an implant unitimplanted in the subject a signal indicative of tongue movement in thesubject, generating a modulation control signal based on the signalindicative of tongue movement, and transmitting the modulation controlsignal from a primary antenna associated with an external unit to asecondary antenna associated with an implant unit.

The method may further include one or more of the following features:determining whether the tongue movement is representative of sleepdisordered breathing, determining whether the sleep disordered breathingincludes an apnea precursor, and determining whether the sleepdisordered breathing includes hypopnea. In addition, the at least oneprocessor may further be configured to determine whether the sleepdisordered breathing includes an hypopnea precursor; the modulationcontrol signal may include a stimulation control signal configured tointeract with the implant unit to cause a contraction in a muscle; andthe signal indicative of tongue movement may be indicative of relativemotion between the primary antenna associated with the external unit andthe secondary antenna associated with the implant unit.

Moreover, the method may include generating a sub-modulation controlsignal for transmission to the implant unit via the primary antenna, anddetecting relative motion between the primary antenna and the secondaryantenna based on determination of a degree of coupling between theprimary antenna and the secondary antenna; the determination of thedegree of coupling may include at least one of a measure of capacitivecoupling, radiofrequency coupling, inductive coupling, or an observationof non-linear behavior in a circuit associated with the implant unit;and adjusting at least one characteristic of the modulation controlsignal based on the signal indicative of tongue movement, the at leastone characteristic of the modulation control signal including voltageamplitude, current amplitude, pulse frequency, or pulse duration.

A device may include at least one pair of modulation electrodesconfigured for implantation in the vicinity of a nerve to be modulatedsuch that the electrodes are spaced apart from one another along alongitudinal direction of the nerve to be modulated. The electrodes maybe further configured to facilitate an electric field in response to anapplied electric signal, the electric field including field linesextending in the longitudinal direction of the nerve to be modulated.The device may further include at least one circuit in electricalcommunication with the at least one pair of modulation electrodes andbeing configured to cause application of the electric signal applied atthe at least one pair of modulation electrodes. A method of modulating anerve may include receiving an alternating current (AC) signal at adevice configured to be implanted into a body of a subject andgenerating a voltage signal in response to the AC signal. The method mayfurther include applying the voltage signal to at least one pair ofmodulation electrodes configured for implantation in the vicinity of thenerve such that the electrodes are spaced apart from one another along alongitudinal direction of the nerve; generating an electrical field inresponse to the voltage signal applied to the at least one pair ofmodulation electrodes, the electric field including field linesextending in a longitudinal direction of the nerve; and modulating thenerve.

A device according to some embodiments may include a primary antennaconfigured to be located external to a subject. The device may alsoinclude at least one processor in electrical communication with theprimary antenna and configured to receive a condition signal from animplantable device, the condition signal indicative of a precursor tosleep disordered breathing, and cause transmission of a primary signalfrom the primary antenna to the implantable device, in response to thecondition signal, to stimulate at least one nerve in response to theprecursor to sleep disordered breathing.

Some embodiments may include a method of detecting a sleep breathingdisorder. The method may include receiving, via a primary antennalocated external to a body of a subject, a condition signal from animplantable device, the condition signal indicating the presence of aprecursor to sleep disordered breathing, and transmitting a primarysignal from the primary antenna to the implantable device, in responseto the condition signal, to stimulate at least one nerve in response tothe occurrence of the precursor to sleep disordered breathing.

A device according to some embodiments may include a primary antennaconfigured to be located external to a subject and at least oneprocessor in electrical communication with the primary antenna. The atleast one processor may be configured to cause transmission of a primarysignal from the primary antenna to an implantable device implanted inthe subject on a genioglossus muscle proximal to a hypoglossal nerve ofthe subject, wherein the implantable device includes at least one pairof modulation electrodes. The at least one processor may be furtherconfigured to adjust one or more characteristics of the primary signalto generate a sub-modulation control signal adapted to cause a currentat the at least one pair of modulation electrodes below a neuromuscularmodulation threshold of the hypoglossal nerve when received by theimplanted device and to generate a modulation control signal adapted tocause a current at the at least one pair of modulation electrodes abovea neuromuscular modulation threshold of the hypoglossal nerve whenreceived by the implantable device.

A device according to some embodiments may include a primary antennaconfigured to be located external to a subject and at least oneprocessor in electrical communication with the primary antenna. The atleast one processor may be configured to cause transmission of a primarysignal from the primary antenna to an implantable device implanted in ablood vessel of a subject in proximity to at least one of a renal nerve,a baroreceptor, and a glossopharyngeal nerve, wherein the implantabledevice includes at least one pair of modulation electrodes. The at leastone processor may be further configured to adjust one or morecharacteristics of the primary signal to generate a sub-modulationcontrol signal adapted to cause a current at the at least one pair ofmodulation electrodes below a neuromuscular modulation threshold of theat least one of a renal nerve, a baroreceptor, and a glossopharyngealnerve when received by the implantable device and to generate amodulation control signal adapted to cause a current at the at least onepair of modulation electrodes above a neuromuscular modulation thresholdat least one of a renal nerve, a baroreceptor, and a glossopharyngealnerve when received by the implantable device.

A device according to some embodiments may include a primary antennaconfigured to be located on the skin of a subject on a substantiallyhairless region of a head of the subject and at least one processor inelectrical communication with the primary antenna. The at least oneprocessor may be configured to cause transmission of a primary signalfrom the primary antenna to an implantable device implanted beneath theskin of the subject, wherein the implantable device includes at leastone pair of modulation electrodes located in a vicinity of an occipitalnerve beneath the skin of the subject in a substantially hairless regionof the head. The at least one processor may be further configured toadjust one or more characteristics of the primary signal to generate asub-modulation control signal adapted to cause a current at the at leastone pair of modulation electrodes below a neuromuscular modulationthreshold of the occipital nerve when received by the implantable deviceand to generate a modulation control signal adapted to cause a currentat the at least one pair of modulation electrodes above a neuromuscularmodulation threshold of the occipital nerve when received by theimplantable device.

A device according to some embodiments may include a primary antennaconfigured to be located external to a subject and at least oneprocessor in electrical communication with the primary antenna. The atleast one processor may be configured to cause transmission of a primarysignal from the primary antenna to an implantable device, wherein theimplantable device includes at least one pair of modulation electrodes.The at least one processor may be further configured to adjust one ormore characteristics of the primary signal to generate a sub-modulationcontrol signal adapted to cause a current at the at least one pair ofmodulation electrodes below a neuromuscular modulation threshold whenreceived by the implantable device and to generate a modulation controlsignal adapted to cause a current at the at least one pair of modulationelectrodes above a neuromuscular modulation threshold when received bythe implantable device.

Some embodiments may include a method of transmitting signals to animplantable device. The method may include determining one or moresub-modulation characteristics of a sub-modulation control signal so asnot to cause a neuromuscular modulation inducing current across at leastone pair of modulation electrodes in electrical communication with animplantable device when the sub-modulation control signal is received bythe implantable device. The method may further include generating themodulation control signal having the one or more modulationcharacteristics and generating the sub-modulation control signal havingthe one or more sub-modulation characteristics. The method may furtherinclude transmitting, via the primary antenna, the modulation controlsignal to a secondary antenna associated with the implantable device andtransmitting, via the primary antenna, the sub-modulation control signalto a secondary antenna associated with the implantable device.

An implant unit according to some embodiments may include a flexiblecarrier, at least one pair of modulation electrodes on the flexiblecarrier, and at least one implantable circuit in electricalcommunication with the at least one pair of modulation electrodes. Theat least one pair of modulation electrodes and the at least one circuitmay be configured for implantation through derma on an underside of asubjects chin and for location proximate to terminal fibers of themedial branch of the subjects hypoglossal nerve. In addition, theimplantable circuit and the electrodes may be configured to cooperate inorder to generate an electric field adapted to modulate one or more ofthe terminal fibers of the medial branch of the hypoglossal nerve.

According to another embodiment of the present disclosure, an implantunit may include a flexible carrier, at least one pair of modulationelectrodes on the flexible carrier, and at least one implantable circuitin electrical communication with the at least one pair of modulationelectrodes. The at least one pair of modulation electrodes and the atleast one circuit may be configured for implantation through derma on anunderside of a subjects chin. The at least one pair of modulationelectrodes may be configured for implantation at a location between thesubject's geniohyoid muscle and the subjects genioglossus muscle and maybe configured to cooperate with the implantable circuit in order togenerate an electric field adapted to cause modulation of the subject'shypoglossal nerve from that location.

According to still another embodiment of the present disclosure, animplant unit may include a flexible carrier, at least one pair ofmodulation electrodes on the flexible carrier, and at least oneimplantable circuit in electrical communication with the at least onepair of modulation electrodes. The at least one pair of modulationelectrodes and the at least one circuit may be configured forintravascular plantation in a subject in a location proximal to at leastone of a renal nerve, a baroreceptor, and a glossopharyngeal nerve, andwherein the implantable circuit and the electrodes may be configured tocooperate in order to generate an electric field adapted to causemodulation of at least a portion of the at least one of a renal artery,a carotid baroreceptor, and a glossopharyngeal nerve.

According to still another embodiment of the present disclosure, animplant unit may include an elongated flexible carrier sized andconfigured for implantation beneath the skin to extend from a firstlocation of a substantially hairless region on one side of a hairline,across a hairline to a second location of a substantially haired regionin a vicinity of an occipital nerve. In addition, the implant unit mayinclude an antenna located on the carrier for implantation in the firstlocation and at least one pair of modulation electrodes configured onthe carrier for implantation in the second location. At least onecircuit may be in electrical communication with the at least one pair ofmodulation electrodes and wherein the implantable circuit and the atleast one pair of modulation electrodes are configured to cooperate inorder to generate an electric field adapted to cause modulation of atleast a portion of the occipital nerve through application of anelectric field.

An implant unit configured for implantation into a body of a subjectaccording to some embodiments may include an antenna configured toreceive a signal. The implant unit may also include at least one pair ofmodulation electrodes configured to be implanted proximal to the tongueof the subject in the vicinity of a hypoglossal nerve, the at least onepair of modulation electrodes may be configured to receive an appliedelectric signal in response to the signal received by the antenna andgenerate an electrical field to modulate the hypoglossal nerve from aposition where the at least one pair of modulation electrodes are spacedapart from the hypoglossal nerve.

An implant unit configured for implantation into a body of a subjectaccording to some embodiments may include an antenna configured toreceive a signal. The implant unit may also include at least one pair ofmodulation electrodes configured to be implanted into the body of thesubject in the vicinity of at least one nerve to be modulated, the atleast one pair of modulation electrodes may be configured to receive anapplied electric signal in response to the signal received by theantenna and generate an electrical field to modulate the at least onenerve from a position where the at least one pair of modulationelectrodes are spaced apart from the at least one nerve.

A hypertension therapy device for affecting blood pressure according tosome embodiments may include an antenna configured to receive a signal.The device may also include at least one pair of modulation electrodesconfigured to be implanted in the blood vessel of the subject in thevicinity at least one of a renal nerve, a carotid baroreceptor, and aglossopharyngeal nerve, the at least one pair of modulation electrodesmay be configured to receive an applied electric signal in response tothe signal received by the antenna and generate an electrical field tomodulate the at least one of a renal nerve, a carotid baroreceptor, anda glossopharyngeal nerve from a position where the at least one pair ofmodulation electrodes are spaced apart from the at least one nerve.

A head pain management device configured for implantation beneath skinof a head of a subject according to some embodiments may include anantenna configured to receive a signal and to be implanted beneath theskin of a subject in a substantially hairless region. The device mayalso include at least one pair of modulation electrodes configured to beimplanted beneath the skin of a subject in a substantially hafted regionand a flexible carrier configured to electrically connect the antennaand the at least one pair of modulation electrodes. In addition, theleast at one pair of modulation electrodes may be configured to receivean applied electric signal in response to the signal received by theantenna and generate an electrical field to modulate an occipital nerveof the subject from a position where the at least one pair of modulationelectrodes are spaced apart from the occipital nerve.

A method of modulating at least one nerve may include receiving analternating current (AC) signal at an implant unit and generating avoltage signal in response to the AC signal. The method may also includeapplying the voltage signal to at least one pair of modulationelectrodes, the at least one pair of modulation electrodes beingconfigured to be implanted into the body of a subject in the vicinity ofthe at least one nerve; and generating an electrical field in responseto the voltage signal applied to the at least one pair of modulationelectrodes to modulate the at least one nerve from a position where theat least one pair of modulation electrodes do not contact the at leastone nerve.

A device according to some embodiments may include an implantablecircuit and at least one pair of implantable electrodes electricallyconnected with the implantable circuit. The circuit and the electrodesmay be configured for implantation in a subject proximal to agenioglossus muscle in the vicinity of a hypoglossal nerve. The circuitmay be configured to deliver to the electrodes an electrical signalhaving a current less than about 1.6 milliamps, and the electrodes maybe configured to emit an electric field such that a portion of the fieldlines extend along a length of the hypoglossal nerve such that thedelivery of the electrical signal of less than about 1.6 milliampscauses modulation of the hypoglossal nerve.

A device according to some embodiments may include an implantablecircuit and at least one pair of implantable electrodes electricallyconnected with the implantable circuit. The circuit and the electrodesmay be configured for implantation in a subject in the vicinity of anerve. The circuit may be configured to deliver to the electrodes anelectrical signal having a current less than about 1.6 milliamps, andthe electrodes may be configured to emit an electric field such that aportion of the field lines extend along a length of the nerve such thatthe delivery of the electrical signal of less than about 1.6 milliampscauses modulation of the nerve.

A device according to some embodiments may include an implantablecircuit and at least one pair of implantable electrodes configured to beimplanted beneath the skin of a subject in a substantially haired regionin the vicinity of an occipital nerve of a subject. The device mayinclude an antenna configured to receive a signal and to be implantedbeneath the skin of the subject in a substantially hairless region. Theimplantable electrodes may be electrically connected with a first end ofthe implantable circuit and the antenna may be electrically connectedwith a second end of the implantable circuit. In addition, the circuitmay be configured to deliver to the electrodes an electrical signalhaving a current less than about 1.6 milliamps, and the electrodes maybe configured to emit an electric field such that a portion of the fieldlines extend along a length of the nerve such that the delivery of theelectrical signal of less than about 1.6 milliamps causes modulation ofthe nerve.

A device according to some embodiments may include an implantablecircuit and at least one pair of implantable electrodes electricallyconnected with the implantable circuit. The circuit and the electrodesmay be configured for implantation in a subject in a blood vessel in thevicinity of at least one of a renal nerve, a carotid baroreceptor, and aglossopharyngeal nerve. The circuit may be configured to deliver to theelectrodes an electrical signal having a current less than about 1.6milliamps, and the electrodes may be configured to emit an electricfield such that a portion of the field lines extend along a length ofthe nerve such that the delivery of the electrical signal of less thanabout 1.6 milliamps causes modulation of the at least one of a renalnerve, a carotid baroreceptor, and a glossopharyngeal nerve.

Some embodiments may include a method of stimulating a nerve via atleast one pair of electrodes associated with an implanted circuit andimplanted in the vicinity of the nerve. The method may includedelivering to the electrodes, via the implanted circuit, an electricalsignal having a current less than about 1.6 milliamps. The method mayfurther include stimulating the nerve via the generation of anelectrical field between the electrodes by the electrical signal havinga current less than about 1.6 milliamps.

A device for regulating energy delivery to an implanted circuit isdisclosed. The device according to some embodiments may include at leastone implantable circuit and at least one pair of implantable electrodesin electrical communication with the circuit. The at least oneimplantable circuit and at least one pair of implantable electrodes maybe configured for implantation in a vicinity of a genioglossus muscle ofa subject. The at least one pair of implantable electrodes may beconfigured to modulate a hypoglossal nerve. The at least one plantablecircuit may be configured deliver a power signal to the at least onepair of implantable electrodes. The power signal may have at least oneof a power level and a duration determined based on a severity of adetected physiologic condition.

The device according to some embodiments may include at least oneimplantable circuit and at least one pair of implantable electrodes inelectrical communication with the circuit. The at least one pair ofimplantable electrodes may be configured to modulate at least one nerve.The at least one implantable circuit may be configured deliver a powersignal to the at least one pair of implantable electrodes. The powersignal may have at least one of a power level and a duration determinedbased on a severity of a detected physiologic condition.

The device according to some embodiments may include a flexible carrierconfigured for implantation in a blood vessel of a subject, at least oneimplantable circuit, and at least one pair of implantable electrodes inelectrical communication with the circuit and located on the carrier.The at least one pair of implantable electrodes being configured tomodulate at least one of a renal nerve, a baroreceptor, and aglossopharyngeal nerve. The at least one implantable circuit may beconfigured deliver a power signal to the at least one pair ofimplantable electrodes. The power signal may have at least one of apower level and a duration determined based on a severity of a detectedphysiologic condition.

Some embodiments may include a method of regulating energy delivery toan implanted circuit for treating a sleep disordered breathingcondition. The method may include detecting a severity of aphysiological condition in a body of a subject and determining, based onthe severity of the physiological condition, at least one of a powerlevel or a duration of a power signal to be delivered by the implantedcircuit to at least one pair of electrodes implanted proximal to ahypoglossal nerve of the subject and in electrical communication withthe implanted circuit. The method may further include delivering thepower signal to the at least one pair of electrodes and the hypoglossalnerve of the subject via the power signal. The method may includedetermining a degree of coupling between a primary antenna associatedwith an external unit and a secondary antenna associated with an implantunit implanted in a body of a subject, and regulating delivery of powerto the implant unit based on the determined degree of coupling.

A device according to some embodiments may include an implantableflexible carrier configured for implantation proximal to a genioglossusmuscle of a subject and a pair of electrodes located on the carrier. Theelectrodes may be spaced from each other by a distance greater than 3mm, and may be configured to facilitate, when supplied with anelectrical signal, a substantially unidirectional electric fieldsufficient to modulate a hypoglossal nerve.

A device according to some embodiments may include an implantableflexible carrier and a pair of electrodes located on the carrier. Theelectrodes may be spaced from each other by a distance greater than 3mm, and may be configured to facilitate, when supplied with anelectrical signal, a substantially unidirectional electric fieldsufficient to modulate at least one nerve.

A device according to some embodiments may include an implantableflexible carrier configured for implantation in a blood vessel of asubject in a vicinity of at least one of a renal nerve, a carotidbaroreceptor, and a glossopharyngeal nerve, and a pair of electrodeslocated on the carrier. The electrodes may be spaced from each other bya distance greater than 3 mm and may be configured to facilitate, whensupplied with an electrical signal, a substantially unidirectionalelectric field sufficient to modulate the at least one of a renal nerve,a carotid baroreceptor, and a glossopharyngeal nerve.

A device according to some embodiments may include an implantableflexible carrier configured for location beneath the skin of a head of asubject, and a pair of electrodes located on the carrier. The electrodesmay be configured for implantation beneath the skin of a substantiallyhaired region of the head of the subject in a vicinity of an occipitalnerve. In addition, the electrodes may be spaced from each other by adistance greater than 3 mm, and may be configured to facilitate, whensupplied with an electrical signal, a substantially unidirectionalelectric field sufficient to modulate the occipital nerve.

A device according to some disclosed embodiments may include a skinpatch configured for temporary affixation on at least one of a neck anda head of a subject. The device may additionally include a primaryantenna associated with the skin patch and at least one processorassociated with the skin patch and configured for electricalcommunication with a power source. The processor may be furtherconfigured to communicate with an implant unit via the primary antennawhen the implant unit is implanted in at least one of the neck and thehead of the subject in a location proximate a hypoglossal nerve, and todetermine a degree of coupling between the primary antenna and asecondary antenna associated with the implant unit, and to regulatedelivery of power from the power source to the implant unit based on thedegree of coupling between the primary antenna and the secondaryantenna.

A device according to some disclosed embodiments may include an externalunit configured for location external to a body of a subject and atleast one processor associated with the external unit and configured forelectrical communication with a power source. The device mayadditionally include a primary antenna associated with the at least oneprocessor. The processor may be configured to communicate with animplant unit when the implant unit is implanted beneath skin of thesubject, to determine a degree of coupling between the primary antennaand a secondary antenna associated with the implant unit, and toregulate delivery of power from the power source to the implant unitbased on the degree of coupling between the primary antenna and thesecondary antenna.

A device according to some disclosed embodiments may include a primaryantenna and a housing configured for location on a body of a subjectproximate to at least one of a renal nerve, a baroreceptor, and aglossopharyngeal nerve. The primary antenna may be associated with thehousing. The device may additionally include at least one processorassociated with the housing and configured for electrical communicationwith a power source. The at least one processor may be furtherconfigured to communicate with an implant unit inserted into a bloodvessel of the subject, to determine a degree of coupling between theprimary antenna and a secondary antenna associated with the implantunit, and to regulate delivery of power from the power source to theimplant unit based on the degree of coupling between the primary antennaand the secondary antenna.

A device according to some disclosed embodiments may include a patchconfigured for placement on a side of a hairline opposite asubstantially haired region of a subject and a primary antennaassociated with the patch. The device may additionally include at leastone processor associated with the patch and configured for electricalcommunication with a power source. The processor may be furtherconfigured to communicate with a modulator including electrodesimplanted in a scalp of the subject, to determine a degree of couplingbetween the primary antenna and a secondary antenna associated with themodulator, and to regulate delivery of power from the power source tothe modulator based on the degree of coupling between the primaryantenna and the secondary antenna.

The device may further include one or more of the following features,either alone or in combination: the external unit may include a skinpatch configured for adherence to the subject's skin; the primaryantenna may include a coil antenna; the external unit may include aflexible substrate; and the at least one processor may be configured toreceive physiologic data via the implant unit and regulate delivery ofpower from the power source to the implant unit based on both thephysiologic data and the degree of coupling between the primary antennaand the secondary antenna, such that the physiologic data may berepresentative of a motion of the implant unit.

In addition, an upper limit of power delivered from the power source tothe implant unit may be determined according to an upper thresholdassociated with the implant unit; a lower limit of power delivered fromthe power source to the implant unit may be determined according to anefficacy threshold of the delivered power; the primary antenna may beconfigured to transmit power to the secondary antenna throughradiofrequency transmission of an alternating current signal; and the atleast one processor may be configured to regulate the delivered power byadjusting at least one of voltage, pulse rate, and current associatedwith the alternating current signal.

The degree of coupling between the primary antenna and the secondaryantenna may include a measure of capacitive coupling, radiofrequencycoupling, inductive coupling, or non-linear behavior in the implantunit; and the measure of non-linear behavior may include at least one ofa measure of a transition to non-linear harmonic behavior and a measureof non-linear harmonic behavior.

A method for regulating delivery of power to an implant unit is alsodisclosed. The method may include communicating with the implant unit,which may be implanted in a body of a subject, determining a degree ofcoupling between a primary antenna associated with a power source and asecondary antenna associated with the implant unit, and regulatingdelivery of power from the power source to the implant unit based on thedegree of coupling.

The method may further include one or more of the following features,either alone or in combination; receiving physiologic data via theimplant unit; regulating delivery of power from the power source to theimplant unit based on the physiologic data and the degree of coupling;and the physiologic data may be representative of a motion of theimplant unit. Moreover, the method may include determining an upperlimit of the power delivered from the power source to the implant unitaccording to an upper threshold associated with the implant unit; anddetermining a lower limit of the power delivered from the power sourceto the implant unit according to an efficacy threshold of the powerdelivered.

In addition, the power may be delivered from the power source to theimplant unit via radiofrequency transmission of an alternating currentsignal; regulating delivery of power from the power source to theimplant unit may comprise adjusting at least one of voltage, pulse rate,and current associated with the alternating current signal; the degreeof coupling between the primary antenna and the secondary antenna mayinclude a measure of capacitive coupling, radiofrequency coupling,inductive coupling, or non-linear behavior in the implant unit, and themeasure of non-linear behavior may include at least one of a measure ofa transition to non-linear harmonic behavior and a measure of non-linearharmonic behavior.

A device according to some embodiments may include a housing configuredfor temporary affixation on at least one of a neck and a head of asubject. The device may also include at least one processor associatedwith the housing and configured for electrical communication with apower source, and an antenna associated with the at least one processor.The at least one processor may be configured to communicate with animplant circuit in at least one of the neck and the head of the subjectin a location proximate a hypoglossal nerve, cause the implant circuitto receive power in a first power mode and in a second power mode,wherein a first level of power delivered in the first power mode is lessthan a second level of power delivered in the second power mode, andwherein during a therapy period, power delivery in the first mode occursover a total time that is greater than about 50% of the therapy period.

A device according to some embodiments may include a housing configuredfor location external to a body of a subject. The device may alsoinclude at least one processor associated with the housing andconfigured for electrical communication with a power source, and anantenna associated with the at least one processor. The at least oneprocessor may be configured to communicate with an implant circuitlocated within the body of the subject, cause the implant circuit toreceive power in a first power mode and in a second power mode, whereina first level of power delivered in the first power mode is less than asecond level of power delivered in the second power mode, and whereinduring a therapy period, power delivery in the first mode occurs over atotal time that is greater than about 50% of the therapy period.

A device according to some embodiments may include a primary antenna anda housing configured for location external to a body of a subject. Thedevice may also include at least one processor associated with thehousing and the primary antenna and configured for electricalcommunication with a power source. The at least one processor may befurther configured to communicate with an implant circuit implanted in ablood vessel of the subject proximate to at least one of a renal nerve,a baroreceptor, and a glossopharyngeal nerve of the subject, cause theimplant circuit to receive power in a first power mode and in a secondpower mode, wherein a first level of power delivered in the first powermode is less than a second level of power delivered in the second powermode, and wherein during a therapy period, power delivery in the firstmode occurs over a total time that is greater than about 50% of thetherapy period.

A device according to some embodiments may include a patch configuredfor placement on a side of a hairline opposite a substantially hairedregion of a head of a subject. The device may also include at least oneprocessor associated with the patch and configured for electricalcommunication with a power source, and a primary antenna associated withthe at least one processor. The at least one processor may be configuredto communicate, via the primary antenna, with a secondary antennalocated beneath the skin of a subject on a side of a hairline opposite asubstantially haired region of the subject, cause an implant circuit toreceive power through the secondary antenna in a first power mode and ina second power mode, wherein a first level of power delivered in thefirst power mode is less than a second level of power delivered in thesecond power mode, and wherein during a therapy period, power deliveryin the first mode occurs over a total time that is greater than about50% of the therapy period.

Some embodiments may include a method of delivering power to animplanted circuit. The method may include communicating with theimplanted circuit, which is implanted in a body of a subject. The methodmay also include transmitting power to the implanted circuit in a firstpower mode and in a second power mode, wherein a first level of powerdelivered in the first power mode is less than a second level of powerdelivered in the second power mode, and wherein during a therapy period,power delivery in the first power mode occurs over a total time that isgreater than about 50% of the therapy period.

A device according to some embodiments of the present disclosureincludes a housing configured to retain a battery, a primary antennaassociated with the housing, and at least one processor in electricalcommunication with the battery and the primary antenna. In someembodiments, the at least one processor may be configured to causetransmission of a primary signal from the primary antenna to an implantunit implanted in at least one of a neck and a head of a subject duringa treatment session of at least three hours in duration, wherein theprimary signal is generated using power supplied by the battery andincludes a pulse train, the pulse train including a plurality ofstimulation pulses.

A device according to some embodiments of the present disclosureincludes a housing configured to retain a battery, a primary antennaassociated with the housing, and at least one processor in electricalcommunication with the battery and the primary antenna. In someembodiments, the at least one processor may be configured to causetransmission of a primary signal from the primary antenna to animplantable device during a treatment session of at least three hours induration, wherein the primary signal is generated using power suppliedby the battery and includes a pulse train, the pulse train including aplurality of stimulation pulses.

A device according to some embodiments of the present disclosureincludes a housing configured to retain a battery, a primary antennaassociated with the housing, and at least one processor in electricalcommunication with the battery and the primary antenna. In someembodiments, the at least one processor may be configured to causetransmission of a primary signal from the primary antenna to animplantable device located in a blood vessel of a subject in a vicinityof at least one of a renal nerve, carotid baroreceptor, andglossopharyngeal nerve of a subject during a treatment session of atleast three hours in duration, wherein the primary signal is generatedusing power supplied by the battery and includes a pulse train, thepulse train including a plurality of stimulation pulses.

A device according to some embodiments of the present disclosureincludes a patch configured for placement on a one side of a hairlineopposite a substantially haired region of a subject, a primary antennaassociated with the patch, and at least one processor associated withthe patch and configured for electrical communication with a battery. Insome embodiments, the at least one processor may be configured to causetransmission of a primary signal from the primary antenna to a secondaryantenna of an implantable device during a treatment session of at leastthree hours in duration, wherein the primary signal is generated usingpower supplied by the battery and includes a pulse train, the pulsetrain including a plurality of modulation pulses.

Additional embodiments consistent with the present disclosure mayinclude a method for delivering electrical modulation treatment pulses.The method may include generating a primary signal in a primary antennausing power supplied by a battery, wherein the primary antenna isassociated with a housing configured to retain the battery. The methodmay further include transmitting the primary signal from the primaryantenna to an implantable device during a treatment session of at leastthree hours in duration, wherein the primary signal includes a pulsetrain and the pulse train includes a plurality of modulation pulses.

A device may include at least one pair of modulation electrodesconfigured for implantation in the vicinity of a nerve to be modulatedsuch that the electrodes are spaced apart from one another along alongitudinal direction of the nerve to be modulated. The electrodes maybe further configured to facilitate an electric field in response to anapplied electric signal, the electric field including field linesextending in the longitudinal direction of the nerve to be modulated.The device may further include at least one circuit in electricalcommunication with the at least one pair of modulation electrodes andbeing configured to cause application of the electric signal applied atthe at least one pair of modulation electrodes. A method of modulating anerve may include receiving an alternating current (AC) signal at adevice configured to be implanted into a body of a subject andgenerating a voltage signal in response to the AC signal. The method mayfurther include applying the voltage signal to at least one pair ofmodulation electrodes configured for implantation in the vicinity of thenerve such that the electrodes are spaced apart from one another along alongitudinal direction of the nerve; generating an electrical field inresponse to the voltage signal applied to the at least one pair ofmodulation electrodes, the electric field including field linesextending in a longitudinal direction of the nerve; and modulating thenerve.

Additional features of the disclosure will be set forth in part in thedescription that follows, and in part will be obvious from thedescription, or may be learned by practice of the disclosed embodiments.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory only,and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments of thedisclosure and, together with the description, serve to explain theprinciples of the embodiments disclosed herein.

FIG. 1 schematically illustrates an implant unit and external unit,according to an exemplary embodiment of the present disclosure.

FIG. 2 is a partially cross-sectioned side view of a subject with animplant unit and external unit, according to an exemplary embodiment ofthe present disclosure.

FIG. 3 schematically illustrates a system including an implant unit andan external unit, according to an exemplary embodiment of the presentdisclosure.

FIG. 4 is a top view of an implant unit, according to an exemplaryembodiment of the present disclosure.

FIG. 5 is a top view of an alternate embodiment of an implant unit,according to an exemplary embodiment of the present disclosure.

FIG. 6 illustrates circuitry of an implant unit and an external unit,according to an exemplary embodiment of the present disclosure.

FIG. 7 illustrates a graph of quantities that may be used in determiningenergy delivery as a function coupling, according to an exemplarydisclosed embodiment.

FIG. 8 depicts a graph illustrating non-linear harmonics.

FIG. 9 depicts a graph of quantities that may be used in determiningenergy delivery as a function coupling, according to an exemplarydisclosed embodiment.

FIG. 10 a illustrates an embodiment wherein electrodes are spaced apartfrom one another in a longitudinal direction of at least a portion of anerve.

FIG. 10 b illustrates an embodiment wherein electrodes are spaced apartfrom one another in a longitudinal direction of at least a portion of anerve.

FIG. 10 c illustrates a situation wherein electrodes are spaced apartfrom one another in a transverse direction of a nerve.

FIG. 11 illustrates effects of electrode configuration on the shape of agenerated electric field.

FIG. 12 depicts anatomy of the tongue and associated muscles and nerves.

FIG. 13 depicts an exemplary implant location for the treatment of sleepapnea.

FIG. 14 depicts an exemplary implant location for the treatment of headpain.

FIG. 15 depicts an exemplary implant location for the treatment ofhypertension.

FIG. 16 depicts an exemplary implant location for the treatment ofhypertension.

FIG. 17 depicts the composition of an exemplary modulation pulse train.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Reference will now be made in detail to exemplary embodiments of thepresent disclosure, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

Embodiments of the present disclosure relate generally to a device forneuromuscular modulation through the delivery of energy. Neuromuscularmodulation may refer to the modulation of nerves, muscles or acombination of both. Muscular modulation may include the stimulation,modification, regulation, or therapeutic alteration of muscularactivity, electrical activity. Muscular modulation may be applieddirectly to a muscle. Nerve modulation, or neural modulation, includesinhibition (e.g. blockage), stimulation, modification, regulation, ortherapeutic alteration of activity, electrical or chemical, in thecentral, peripheral, or autonomic nervous system. Nerve modulation maytake the form of nerve stimulation, which may include providing energyto the nerve to create a voltage change sufficient for the nerve toactivate, or propagate an electrical signal of its own. Nerve modulationmay also take the form of nerve inhibition, which may includingproviding energy to the nerve sufficient to prevent the nerve frompropagating electrical signals. Nerve inhibition may be performedthrough the constant application of energy, and may also be performedthrough the application of enough energy to inhibit the function of thenerve for some time after the application. Other forms of neuralmodulation may modify the function of a nerve, causing a heightened orlessened degree of sensitivity. As referred to herein, modulation of anerve may include modulation of an entire nerve and/or modulation of aportion of a nerve. For example, modulation of a motor neuron may beperformed to affect only those portions of the neuron that are distal ofthe location to which energy is applied. Furthermore, implant unit 110may be configured to not perform any modulation at all. Implant unit 110may be configured to measure physiological data, for example throughsensors or other measuring devices. For example, implant unit 110 mayinclude sensors to detect a level of glucose in a subject, suchinformation may be communicated to external unit 120 through variousmeans as described herein. Some of the exemplary embodiments describedherein refer to neural modulation. It will be understood that many ofthe exemplary techniques, devices, and methods disclosed may also beapplied directly to muscles to cause muscular modulation.

In patients with OSA, for example, a primary target response of nervestimulation may include contraction of a tongue muscle (e.g., thegenioglossus muscle) in order to move the tongue to a position that doesnot block the patient's airway, e.g. away from the pharyngeal wall. Inthe treatment of migraine headaches, nerve inhibition may be used toreduce or eliminate the sensation of pain. In the treatment ofhypertension, neural modulation may be used to increase, decrease,eliminate or otherwise modify nerve signals generated by the body toregulate blood pressure.

While embodiments of the present disclosure may be disclosed for use inpatients with specific conditions, the embodiments may be used inconjunction with any patient/portion of a body where nerve modulationmay be desired. That is, in addition to use in patients with OSA,migraine headaches, or hypertension, embodiments of the presentdisclosure may be use in many other areas, including, but not limitedto: deep brain stimulation (e.g., treatment of epilepsy, Parkinson's,and depression); cardiac pace-making, stomach muscle stimulation (e.g.,treatment of obesity), back pain, incontinence, menstrual pain, and/orany other condition that may be affected by neural modulation.

FIG. 1 illustrates an implant unit and external unit, according to anexemplary embodiment of the present disclosure. An implant unit 110, maybe configured for implantation in a subject, in a location that permitsit to modulate a nerve 115. The implant unit 110 may be located in asubject such that intervening tissue 111 exists between the implant unit110 and the nerve 115. Intervening tissue may include muscle tissue,connective tissue, organ tissue, or any other type of biological tissue.Thus, location of implant unit 110 does not require contact with nerve115 for effective neuromodulation. A more detailed discussion of noncontacting neuromodulation is provided below with respect to FIGS. 10 a,10 b, 10 c, and 11. The implant unit 110 may also be located directlyadjacent to nerve 115, such that no intervening tissue 111 exists.

In treating OSA, implant unit 110 may be located on a genioglossusmuscle of a patient. Such a location is suitable for modulation of thehypoglossal nerve, branches of which run inside the genioglossus muscle.Further details regarding implantation locations of an implant unit 110for treatment of OSA are provided below with respect to FIGS. 12 and 13.Implant unit 110 may also be configured for placement in otherlocations. For example, migraine treatment may require subcutaneousimplantation in the back of the neck, near the hairline of a subject, orbehind the ear of a subject, to modulate the greater occipital nerve,lesser occipital nerve, and/or the trigeminal nerve. Further detailsregarding implantation locations of an implant unit 110 for treatment ofhead pain, such as migraine headaches, are provided below with respectto FIG. 14. Treating hypertension may require the implantation of aneuromodulation implant intravascularly inside the renal artery or renalvein (to modulate the parasympathetic renal nerves), either unilaterallyor bilaterally, inside the carotid artery or jugular vein (to modulatethe glossopharyngeal nerve through the carotid baroreceptors).Alternatively or additionally, treating hypertension may require theimplantation of a neuromodulation implant subcutaneously, behind the earor in the neck, for example, to directly modulate the glossopharyngealnerve. Further details regarding implantation locations of an implantunit 110 for treatment of hypertension are provided below, with respectto FIGS. 15 and 16.

External unit 120 may be configured for location external to a patient,either directly contacting, or close to the skin 112 of the patient.External unit 120 may be configured to be affixed to the patient, forexample, by adhering to the skin 112 of the patient, or through a bandor other device configured to hold external unit 120 in place. Adherenceto the skin of external unit 120 may occur such that it is in thevicinity of the location of implant unit 110.

FIG. 2 illustrates an exemplary embodiment of a neuromodulation systemfor delivering energy in a patient 100 with OSA. The system may includean external unit 120 that may be configured for location external to thepatient. As illustrated in FIG. 2, external unit 120 may be configuredto be affixed to the patient 100. FIG. 2 illustrates that in a patient100 with OSA, the external unit 120 may be configured for placementunderneath the patient's chin and/or on the front of patient's neck. Thesuitability of placement locations may be determined by communicationbetween external unit 120 and implant unit 110, discussed in greaterdetail below. In alternate embodiments, for the treatment of conditionsother than OSA, the external unit may be configured to be affixedanywhere suitable on a patient, such as the back of a patient's neck,e.g. for communication with a migraine treatment implant unit, on theouter portion of a patient's abdomen, e.g. for communication with astomach modulating implant unit, on a patient's back, e.g. forcommunication with a renal artery modulating implant unit, and/or on anyother suitable external location on a patient's skin, depending on therequirements of a particular application.

External unit 120 may further be configured to be affixed to analternative location proximate to the patient. For example, in oneembodiment, the external unit may be configured to fixedly or removablyadhere to a strap or a band that may be configured to wrap around a partof a patient's body. Alternatively, or in addition, the external unitmay be configured to remain in a desired location external to thepatient's body without adhering to that location.

The external unit 120 may include a housing. The housing may include anysuitable container configured for retaining components. In addition,while the external unit is illustrated schematically in FIG. 2, thehousing may be any suitable size and/or shape and may be rigid orflexible. Non-limiting examples of housings for the external unit 100include one or more of patches, buttons, or other receptacles havingvarying shapes and dimensions and constructed of any suitable material.In one embodiment, for example, the housing may include a flexiblematerial such that the external unit may be configured to conform to adesired location. For example, as illustrated in FIG. 2, the externalunit may include a skin patch, which, in turn, may include a flexiblesubstrate. The material of the flexible substrate may include, but isnot limited to, plastic, silicone, woven natural fibers, and othersuitable polymers, copolymers, and combinations thereof. Any portion ofexternal unit 120 may be flexible or rigid, depending on therequirements of a particular application.

As previously discussed, in some embodiments external unit 120 may beconfigured to adhere to a desired location. Accordingly, in someembodiments, at least one side of the housing may include an adhesivematerial. The adhesive material may include a biocompatible material andmay allow for a patient to adhere the external unit to the desiredlocation and remove the external unit upon completion of use. Theadhesive may be configured for single or multiple uses of the externalunit. Suitable adhesive materials may include, but are not limited tobiocompatible glues, starches, elastomers, thermoplastics, andemulsions. The housing may also be removably affixed to skin of asubject through alternate means, such as straps or bands. Any of thevarious elements described herein as associated with the external unitmay be located on or off the housing, as appropriate. For example, ahousing comprising a patch may include a processor and a primaryantenna.

FIG. 3 schematically illustrates a system including external unit 120and an implant unit 110. In some embodiments, internal unit 110 may beconfigured as a unit to be implanted into the body of a patient, andexternal unit 120 may be configured to send signals to and/or receivesignals from implant unit 110.

As shown in FIG. 3, various components may be included within a housingof external unit 120 or otherwise associated with external unit 120. Asillustrated in FIG. 3, at least one processor 144 may be associated withexternal unit 120. For example, the at least one processor 144 may belocated within the housing of external unit 120. In alternativeembodiments, the at least one processor may be configured for wired orwireless communication with the external unit from a location externalto the housing.

The at least one processor may include any electric circuit that may beconfigured to perform a logic operation on at least one input variable.The at least one processor may therefore include one or more integratedcircuits, microchips, microcontrollers, and microprocessors, which maybe all or part of a central processing unit (CPU), a digital signalprocessor (DSP), a field programmable gate array (FPGA), or any othercircuit known to those skilled in the art that may be suitable forexecuting instructions or performing logic operations.

FIG. 3 illustrates that the external unit 120 may further be associatedwith a power source 140. The power source may be removably couplable tothe external unit at an exterior location relative to external unit.Alternatively, as shown in FIG. 3, power source 140 may be permanentlyor removably coupled to a location within external unit 120. The powersource may further include any suitable source of power configured to bein electrical communication with the processor. In one embodiment, forexample the power source 140 may include a battery. In some embodiments,external unit 120 may include a housing configured to retain a powersource, such as a battery. As further detailed below, embodiments of theneuromodulation techniques disclosed herein permit neuromodulation atlow power consumption levels. Thus, in some embodiments, a batteryserving as a power source may have a capacity of less than 60milliamp-hours, less than 120 milliamp-hours, and less than 240milliamp-hours.

The power source may be configured to power various components withinthe external unit. As illustrated in FIG. 3, power source 140 may beconfigured to provide power to the processor 144. In addition, the powersource 140 may be configured to provide power to a signal source 142.The signal source 142 may be in communication with the processor 144 andmay include any device configured to generate a signal (e.g., asinusoidal signal, square wave, triangle wave, microwave,radio-frequency (RF) signal, or any other type of elect ° magneticsignal). Signal source 142 may include, but is not limited to, awaveform generator that may be configured to generate alternatingcurrent (AC) signals and/or direct current (DC) signals. In oneembodiment, for example, signal source 142 may be configured to generatean AC signal for transmission to one or more other components. Signalsource 142 may be configured to generate a signal of any suitablefrequency. In some embodiments, signal source 142 may be configured togenerate a signal having a frequency of from about 6.5 MHz to about 13.6MHz. In additional embodiments, signal source 142 may be configured togenerate a signal having a frequency of from about 7.4 to about 8.8 MHz.In further embodiments, signal source 142 may generate a signal having afrequency as low as 90 kHz or as high as 28 MHz.

Signal source 142 may be configured for direct or indirect electricalcommunication with an amplifier 146. The amplifier may include anysuitable device configured to amplify one or more signals generated fromsignal source 142. Amplifier 146 may include one or more of varioustypes of amplification devices, including, for example, transistor baseddevices, operational amplifiers, RF amplifiers, power amplifiers, or anyother type of device that can increase the gain associated one or moreaspects of a signal. The amplifier may further be configured to outputthe amplified signals to one or more components within external unit120.

FIG. 3 further illustrates that external unit 120 may be associated withan indicator 145. That is, indicator 145 may be removably or permanentlyattached to external unit 120. In one embodiment, for example, indicator145 may be located within external unit 120. Alternatively, indicator145 may be in wired or wireless communication with external unit 120from a location external to external unit 120.

The indicator 145 may include any suitable device configured to providea signal to the user and/or may include any suitable signal outputelements configured to communicate with a user. Suitable signal outputelements may include, but are not limited to, audible, visual, andtactile outputs. In one embodiment, for example, the signal output meansmay include an electrical signal configured to communicate with theimplant unit 110. That is, the electrical signal may cause the implantunit 110 to stimulate a nerve and/or induce one of a proprioceptive orkinesthesic reaction in the user. Thus, in the context of an implantunit 110 located in the genioglosssus, processor 144 may be configuredto function as the indicator 145 to cause a modulation of a nervelocated within the tongue by the implant unit 110 (e.g. the processormay provide the signal that causes a physiological indication to theuser). In other embodiments, the indicator 145 may be configured to emitan audible signal, including one or more tones. The indicator 145 mayalso or alternatively be configured with lighting elements (e.g., LEDs,etc.) for providing various visual signals to a user. Additionally oralternatively, the indicator 145 may include a device configured tovibrate as part of an alert issued to the user. It should be understoodthat any combination of these or other suitable signaling elements maybe included in the indicator 145 associated with external unit 120.

The indicator 145 may further include any suitable antenna known tothose skilled in the art and may be configured to send and receivesignals to a user in order to alert the user of a condition relating tothe external unit 120 and/or implant unit 110. In one embodiment, forexample, the indicator 145 may be configured to provide a variablesignal according to a distance between the external unit 120 and theimplant unit 110.

The indicator 145 may be configured to permit a user to place theexternal unit 120 at an optimal location in relation to the implant unit110. For example, a user interested in placing external unit 120 on theskin, for example, in the vicinity of implant 110 may proceed to moveexternal unit 120 around in the general vicinity of implant unit 110.When external unit 120 is placed in a location where a suitableconnection can be achieved between external unit 120 and implant unit110 (e.g., a suitable coupling connection), the indicator 145 may alertthe user of this condition. The indicator 145 may further be configuredto alert the user of the degree of connectivity between external unit120 and implant unit 110 such that the user may be able to place theexternal unit in a location where the connection between the two unitsis at or near a maximum level.

One or more functions associated with the indicator 145 may be providedby a processor associated with external unit 120. For example, amongother functions, a processor may be configured to monitor a connectionstrength between external unit 120 and implant unit 110 and issue acontrol signal to cause the indicator 145 to activate.

The external unit may additionally include a primary antenna 150. Theprimary antenna may be configured as part of a circuit within externalunit 120 and may be coupled either directly or indirectly to variouscomponents in external unit 120. The primary antenna may be configuredfor location external to a subject. For example, as shown in FIG. 3,primary antenna 150 may be configured for communication with theamplifier 146.

The primary antenna may include any conductive structure that may beconfigured to create an electromagnetic field. The primary antenna mayfurther be of any suitable size, shape, and/or configuration. Theprimary antenna may be flexible to an extent permitting it to generallyconform to the contours of a subject's skin. The size, shape, and/orconfiguration may be determined by the size of the patient, theplacement location of the implant unit, the size and/or shape of theimplant unit, the amount of energy required to modulate a nerve, alocation of a nerve to be modulated, the type of receiving electronicspresent on the implant unit, etc. The primary antenna may include anysuitable antenna known to those skilled in the art that may beconfigured to send and/or receive signals. Suitable antennas mayinclude, but are not limited to, a long-wire antenna, a patch antenna, ahelical antenna, etc. In one embodiment, for example, as illustrated inFIG. 3, primary antenna 150 may include a coil antenna. Such a coilantenna may be made from any suitable conductive material and may beconfigured to include any suitable arrangement of conductive coils(e.g., diameter, number of coils, layout of coils, etc.). A coil antennasuitable for use as primary antenna 150 may have a diameter of betweenabout 1 cm and 10 cm, and may be circular or oval shaped. In someembodiments, a coil antenna may have a diameter between 5 cm and 7 cm,and may be oval shaped. A coil antenna suitable for use as primaryantenna 150 may have any number of windings, e.g. 4, 8, 12, or more. Acod antenna suitable for use as primary antenna 150 may have a wirediameter between about 0.1 mm and 2 mm. These antenna parameters areexemplary only, and may be adjusted above or below the ranges given toachieve suitable results.

As noted, implant unit 110 may be configured to be implanted in apatient's body (e.g., beneath the patient's skin). FIG. 2 illustratesthat the implant unit 110 may be configured to be implanted formodulation of a nerve associated with a muscle of the subject's tongue130. Modulating a nerve associated with a muscle of the subject's tongue130 may include stimulation to cause a muscle contraction. In furtherembodiments, the implant unit may be configured to be placed inconjunction with any nerve that one may desire to modulate. For example,modulation of the occipital nerve, the greater occipital nerve, and/orthe trigeminal nerve may be useful for treating pain sensation in thehead, such as that from migraines. Modulation of parasympathetic nervefibers on and around the renal arteries (i.e. the renal nerves), thevagus nerve, and/or the glossopharyngeal nerve may be useful fortreating hypertension. Additionally, any nerve of the peripheral nervoussystem (both spinal and cranial), including motor neurons, sensoryneurons, sympathetic neurons and parasympathetic neurons, may bemodulated to achieve a desired effect.

Implant unit 110 may be formed of any materials suitable forimplantation into the body of a patient. In some embodiments, implantunit 110 may include a flexible carrier 161 (FIG. 4) including aflexible, biocompatible, material and/or insulative material. Suchmaterials may include, for example, silicone, polyimides,phenyltrimethoxysilane (PTMS), polymethyl methacrylate (PMMA), ParyleneC, polyimide, liquid polyimide, laminated polyimide, black epoxy,polyether ether ketone (PEEK), Liquid Crystal Polymer (LCP), Kapton,etc. Implant unit 110 may further include circuitry including conductivematerials, such as gold, platinum, titanium, or any other biocompatibleconductive material or combination of materials. Implant unit 110 andflexible carrier 161 may also be fabricated with a thickness suitablefor implantation under a patient's skin. Implant 110 may have thicknessof less than about 4 mm or less than about 2 mm.

Other components that may be included in or otherwise associated withthe implant unit are illustrated in FIG. 3. For example, implant unit110 may include a secondary antenna 152 mounted onto or integrated withflexible carrier 161. Similar to the primary antenna, the secondaryantenna may include any suitable antenna known to those skilled in theart that may be configured to send and/or receive signals. The secondaryantenna may include any suitable size, shape, and/or configuration. Thesize, shape and/or configuration may be determined by the size of thepatient, the placement location of the implant unit, the amount ofenergy required to modulate the nerve, etc. Suitable antennas mayinclude, but are not limited to, a long-wire antenna, a patch antenna, ahelical antenna, etc. In some embodiments, for example, secondaryantenna 152 may include a coil antenna having a circular shape (see alsoFIG. 4) or oval shape. Such a coil antenna may be made from any suitableconductive material and may be configured to include any suitablearrangement of conductive cons (e.g., diameter, number of coils, layoutof cons, etc.). A coil antenna suitable for use as secondary antenna 152may have a diameter of between about 5 mm and 30 mm, and may be circularor oval shaped. A coil antenna suitable for use as secondary antenna 152may have any number of windings, e.g. 4, 15, 20, 30, or 50. A coilantenna suitable for use as secondary antenna 152 may have a wirediameter between about 0.01 mm and 1 mm. These antenna parameters areexemplary only, and may be adjusted above or below the ranges given toachieve suitable results.

Implant unit 110 may additionally include a plurality offield-generating implant electrodes 158 a, 158 b. The electrodes mayinclude any suitable shape and/or orientation on the implant unit solong as the electrodes may be configured to generate an electric fieldin the body of a patient. Like implant unit 110, implant electrodes 158a and 158 b may be configured for implantation into the body of asubject in the vicinity of one or more nerves either together with orseparate from implant unit 110. Implant electrodes 158 a and 158 b mayalso include any suitable conductive material (e.g., copper, silver,gold, platinum, iridium, platinum-iridium, platinum-gold, conductivepolymers, etc.) or combinations of conductive (and/or noble metals)materials. In some embodiments, for example, the electrodes may includeshort line electrodes, point electrodes, circular electrodes, and/orcircular pairs of electrodes. As shown in FIG. 4, electrodes 158 a and158 b may be located on an end of a first extension 162 a of an elongatearm 162. The electrodes, however, may be located on any portion ofimplant unit 110. Additionally, implant unit 110 may include electrodeslocated at a plurality of locations, for example on an end of both afirst extension 162 a and a second extension 162 b of elongate arm 162,as illustrated, for example, in FIG. 5. Electrodes on different sides ofimplant unit 110 may be activated sequentially or simultaneously togenerate respective electric fields. Implant electrode pairs may bespaced apart from one another along the longitudinal direction by adistance of less than about 25 mm. Implant electrodes may have athickness between about 200 nanometers and 1 millimeter, and may have asurface area of about 0.01 mm² to about 80 mm². Anode and cathodeelectrode pairs may be spaced apart by about a distance of about 0.2 mmto 25 mm. In additional embodiments, anode and cathode electrode pairsmay be spaced apart by a distance of about 1 mm to 10 mm, or between 4mm and 7 mm. In other embodiments, anode and cathode electrode pairs maybe spaced apart by a distance of approximately 3 mm. In still otherembodiments, anode and cathode electrode pairs may be spaced from eachother by a distance greater than about 3 mm.

Adjacent anodes or adjacent cathodes may be spaced apart by distances assmall as 0.001 mm or less, or as great as 25 mm or more. In someembodiments, adjacent anodes or adjacent cathodes may be spaced apart bya distance between about 0.2 mm and 1 mm.

As noted, electrodes 158 a and 158 b may configured to be implanted intothe body of a subject in the vicinity of at least one nerve to bemodulated. Implant (or modulation) electrodes 158 a and 158 b may beconfigured to receive an applied electric signal in response to thesignal received by the antenna and generate an electrical field tomodulate the at least one nerve from a position where the at least onepair of modulation electrodes does not contact the at least one nerve.

FIG. 4 provides a schematic representation of an exemplary configurationof implant unit 110. As illustrated in FIG. 4, in one embodiment, thefield-generating electrodes 158 a and 158 b may include two sets of fourcircular electrodes, provided on flexible carrier 161, with one set ofelectrodes providing an anode and the other set of electrodes providinga cathode. Implant unit 110 may include one or more structural elementsto facilitate implantation of implant unit 110 into the body of apatient. Such elements may include, for example, elongated arms, sutureholes, polymeric surgical mesh, biological glue, spikes of flexiblecarrier protruding to anchor to the tissue, spikes of additionalbiocompatible material for the same purpose, etc. that facilitatealignment of implant unit 110 in a desired orientation within apatient's body and provide attachment points for securing implant unit110 within a body (e.g., for attaching flexible carrier 161 to a surfaceof non-nerve tissue within the body of a subject). For example, in someembodiments, implant unit 110 may include an elongate arm 162 having afirst extension 162 a and, optionally, a second extension 162 b.Extensions 162 a and 162 b may aid in orienting implant unit 110 withrespect to a particular muscle (e.g., the genioglossus muscle), a nervewithin a patient's body, or a surface within a body above a nerve. Forexample, first and second extensions 162 a, 162 b may be configured toenable the implant unit to conform at least partially around soft orhard tissue (e.g., nerve, bone, or muscle, etc.) beneath a patient'sskin. Further, implant unit 110 may also include one or more sutureholes 160 located anywhere on flexible carrier 161. For example, in someembodiments, suture holes 160 may be placed on second extension 162 b ofelongate arm 162 and/or on first extension 162 a of elongate arm 162.Implant unit 110 may be constructed in various shapes. In someembodiments, implant unit may appear substantially as illustrated inFIG. 4. In other embodiments, implant unit 110 may lack illustratedstructures such as second extension 162 b, or may have additional ordifferent structures in different orientations. Additionally, implantunit 110 may be formed with a generally triangular, circular, orrectangular shape, as an alternative to the winged shape shown in FIG.4. In some embodiments, the shape of implant unit 110 (e.g., as shown inFIG. 4) may facilitate orientation of implant unit 110 with respect to aparticular nerve to be modulated. Thus, other regular or regular shapesmay be adopted in order to facilitate implantation in differing parts ofthe body. For example, flexible carrier 161 may facilitate orientationof implant unit 110 with respect to the contour of a particular tissue.Such tissue may include any combination of muscle tissue, bone,connective tissue, adipose tissue, or organ tissue. For subjectssuffering from obstructive sleep apnea, for instance, implant unit 110may be configured to adapt to the contour of the genioglossus muscle.

As illustrated in FIG. 4, secondary antenna 152, circuitry 180, andelectrodes 158 a, 158 b may be mounted on or integrated with flexiblecarrier 161. Various circuit components and connecting wires (discussedfurther below) may be used to connect secondary antenna with implantelectrodes 158 a and 158 b. To protect the antenna, electrodes, circuitcomponents, and connecting wires from the environment within a patient'sbody, implant unit 110 may include a protective coating thatencapsulates implant unit 110. In some embodiments, the protectivecoating may be made from a flexible material to enable bending alongwith flexible carrier 161. The encapsulation material of the protectivecoating may also resist humidity penetration and protect againstcorrosion. In some embodiments, the protective coating may includesilicone, polyimides, phenyltrimethoxysilane (PTMS), polymethylmethacrylate (PMMA), Parylene C, liquid polyimide, laminated polyimide,polyimide, Kapton, black epoxy, polyether ketone (PEEK), Liquid CrystalPolymer (LCP), or any other suitable biocompatible coating. In someembodiments, the protective coating may include a plurality of layers,including different materials or combinations of materials in differentlayers.

FIG. 5 is a perspective view of an alternate embodiment of an implantunit 110, according to an exemplary embodiment of the presentdisclosure. As illustrated in FIG. 5, implant unit 110 may include aplurality of electrodes, located, for example, at the ends of firstextension 162 a and second extension 162 b. FIG. 5 illustrates anembodiment wherein implant electrodes 158 a and 158 b include short lineelectrodes.

Returning to FIGS. 2 and 3, external unit 120 may be configured tocommunicate with implant unit 110. The at least one processor 144 may beconfigured to cause transmission of a primary signal from the primaryantenna to implant unit 110, or any other implantable device includingat least one pair of modulation electrodes. For example, in someembodiments, a primary signal may be generated on primary antenna 150,using, e.g., processor 144, signal source 142, and amplifier 146. Morespecifically, in one embodiment, power source 140 may be configured toprovide power to one or both of the processor 144 and the signal source142. The processor 144 may be configured to cause signal source 142 togenerate a signal (e.g., an RF energy signal). Signal source 142 may beconfigured to output the generated signal to amplifier 146, which mayamplify the signal generated by signal source 142. The amount ofamplification and, therefore, the amplitude of the signal may becontrolled, for example, by processor 144. The amount of gain oramplification that processor 144 causes amplifier 146 to apply to thesignal may depend on a variety of factors, including, but not limitedto, the shape, size, and/or configuration of primary antenna 150, thesize of the patient, the location of implant unit 110 in the patient,the shape, size, and/or configuration of secondary antenna 152, a degreeof coupling between primary antenna 150 and secondary antenna 152(discussed further below), a desired magnitude of electric field to begenerated by implant electrodes 158 a, 158 b, etc. Amplifier 146 mayoutput the amplified signal to primary antenna 150.

At least one processor 144 may also be configured to receive a conditionsignal from an implantable device such as implant unit 110. A conditionsignal may be any type of signal received by the at least one processor,for example via primary antenna 144, from an implantable device. Acondition signal may be indicative of movement of the implantabledevice, location of the implantable device, a maximum power limit of theimplantable device, and/or a minimum efficacy threshold of theimplantable device. The condition signal may also be indicative of adegree of coupling between primary antenna 144 and secondary antenna152. A condition signal may include a primary coupled signal componentpresent on the primary antenna due to signals within the implant. Acondition signal may also include a signal generated by the implantabledevice itself, for example, by at least one processor associated theimplant. A condition signal may be generated by the implant in responseto information generated by the implant, information pertaining to theinternal state of the implant, and/or information received by sensorsassociated with the implant. Various examples of the nature and form ofa condition signal are expressed in more detail belo.

External unit 120 may communicate a primary signal on primary antenna tothe secondary antenna 152 of implant unit 110. This communication mayresult from coupling between primary antenna 150 and secondary antenna152. Such coupling of the primary antenna and the secondary antenna mayinclude any interaction between the primary antenna and the secondaryantenna that causes a signal on the secondary antenna in response to asignal applied to the primary antenna. In some embodiments, couplingbetween the primary and secondary antennas may include capacitivecoupling, inductive coupling, radiofrequency coupling, a measure ofharmonic resonance in the implant, etc. and any combinations thereof.

A degree of coupling between primary antenna 150 and secondary antenna152 may depend on the proximity of the primary antenna relative to thesecondary antenna. As used herein, the term “degree of coupling,” mayinclude any measure of electromagnetic interaction between two antennas.For example, a degree of coupling may include a measure of efficiency ofenergy transfer between two antennas (e.g. primary antenna 150 andsecondary antenna 152), a measure of signal strength, a measure ofsignal arrival time, a measure of travel time of signals between twoantennas, and/or any other measure of communication between twoantennas. By way of example only, a degree of coupling may be measuredin terms of current, voltage, power, elapsed time, arrival time,frequency, phase, one or more ratios of the foregoing, or any otherindicator of communication that can be quantified. A degree of couplingbetween primary antenna 150 and secondary antenna 152 may depend on theproximity of the primary antenna to the secondary antenna. The proximityof the primary and secondary antennas may be expressed in terms of acoaxial offset (e.g., a distance between the primary and secondaryantennas when central axes of the primary and secondary antennas areco-aligned), a lateral offset (e.g., a distance between a central axisof the primary antenna and a central axis of the secondary antenna),and/or an angular offset (e.g., an angular difference between thecentral axes of the primary and secondary antennas). In someembodiments, a theoretical maximum efficiency of coupling may existbetween primary antenna 150 and secondary antenna 152 when both thecoaxial offset, the lateral offset, and the angular offset are zero.Increasing any of the coaxial offset, the lateral offset, and theangular offset may have the effect of reducing the efficiency or degreeof coupling between primary antenna 150 and secondary antenna 152.

As a result of coupling between primary antenna 150 and secondaryantenna 152, a secondary signal may arise on secondary antenna 152 whenthe primary signal is present on the primary antenna 150. Such couplingmay include inductive/magnetic coupling, RF coupling/transmission,capacitive coupling, or any other mechanism where a secondary signal maybe generated on secondary antenna 152 in response to a primary signalgenerated on primary antenna 150. Coupling may refer to any interactionbetween the primary and secondary antennas. In addition to the couplingbetween primary antenna 150 and secondary antenna 152, circuitcomponents associated with implant unit 110 may also affect thesecondary signal on secondary antenna 152. Thus the secondary signal onsecondary antenna 152 may refer to any and all signals and signalcomponents present on secondary antenna 152 regardless of the source.

While the presence of a primary signal on primary antenna 150 may causeor induce a secondary signal on secondary antenna 152, the couplingbetween the two antennas may also lead to a coupled signal or signalcomponents on the primary antenna 150 as a result of the secondarysignal present on secondary antenna 152. A signal on primary antenna 150induced by a secondary signal on secondary antenna 152 may be referredto as a primary coupled signal component. The primary signal may referto any and all signals or signal components present on primary antenna150, regardless of source and the primary coupled signal component mayrefer to any signal or signal component arising on the primary antennaas a result of coupling with signals present on secondary antenna 152.Thus, in some embodiments, the primary coupled signal component maycontribute to the primary signal on primary antenna 150.

Implant unit 110 may be configured to respond to external unit 120. Forexample, in some embodiments, a primary signal generated on primary coil150 may cause a secondary signal on secondary antenna 152, which inturn, may cause one or more responses by implant unit 110. In someembodiments, the response of implant unit 110 may include the generationof an electric field between implant electrodes 158 a and 158 b. Forexample, at least one processor 144 may be configured to adjust one ormore characteristics of the primary signal to generate either or both ofa sub-modulation control signal and a modulation control signal whenreceived by the an implantable device. Adjusted characteristics of amodulation control signal may be referred to as modulationcharacteristics, whereas adjusted characteristics of a sub-modulationcontrol signal may be referred to as sub-modulation characteristics. Thesecondary signal on secondary antenna 152 caused by the primary signalmay include a modulation control signal, adapted to cause the generationof an electric field sufficient to cause a neuromuscular inducingcurrent across the electrodes of implant unit 110. Additionally, thesecondary signal on secondary antenna 152 caused by the primary signalmay be a sub-modulation control signal, adapted so as not to cause thegeneration of an electric field sufficient to cause a neuromuscularinducing current across electrodes of implant unit 110. The adjustedcharacteristics are explained in greater detail below.

FIG. 6 illustrates circuitry 170 that may be included in external unit120 and circuitry 180 that may be included in implant unit 110 orotherwise associated with implant unit 110. For example, circuitry 180may be included with implant unit 110 (e.g., provided on flexiblecarrier 161) or may be included on a substrate or implant elementseparate from implant unit 110, Additional, different, or fewer circuitcomponents may be included in either or both of circuitry 170 andcircuitry 180. As shown in FIG. 6, secondary antenna 152 may be arrangedin electrical communication with implant electrodes 158 a, 158 b. Insome embodiments, circuitry 180 connecting secondary antenna 152 withimplant electrodes 158 a and 158 b may cause a voltage potential acrossimplant electrodes 158 a and 158 b in the presence of a secondary signalon secondary antenna 152. For example, an implant unit 110 may apply avoltage potential to implant electrodes 158 a and 158 b in response toan AC signal received by secondary antenna 152. As used herein, the term“voltage potential” may include a voltage signal or any electricalsignal. This voltage potential may be referred to as a field inducingsignal, as this voltage potential may generate an electric field betweenimplant electrodes 158 a and 158 b. More broadly, the field inducingsignal may include any signal (e.g., voltage potential) applied toelectrodes associated with the implant unit that may result in anelectric field being generated between the electrodes.

The field inducing signal may be generated as a result of conditioningof the secondary signal by circuitry 180. As shown in FIG. 6, circuitry170 of external unit 120 may be configured to generate an AC primarysignal on primary antenna 150 that may cause an AC secondary signal onsecondary antenna 152 in circuitry 180. In certain embodiments, however,it may be advantageous (e.g., in order to generate a unidirectionalelectric field for modulation of a nerve) to provide a DC field inducingsignal at implant electrodes 158 a and 158 b. To convert the ACsecondary signal on secondary antenna 152 to a DC field inducing signal,circuitry 180 in implant unit 110 may include a signal modifier, forexample, an AC-DC converter. The AC to DC converter may include anysuitable converter known to those skilled in the art. For example, insome embodiments the AC-DC converter may include rectification circuitcomponents including, for example, diode 156 and appropriate capacitorsand resistors. In alternative embodiments, implant unit 110 may includean AC-AC converter, or no converter, in order to provide an AC fieldinducing signal at implant electrodes 158 a and 158 b.

As noted above, the field inducing signal may be configured to generatean electric field between implant electrodes 158 a and 158 b. In someinstances, the magnitude, orientation, energy density, and/or durationof the generated electric field resulting from the field inducing signalmay cause current flow sufficient to modulate one or more nerves in thevicinity of electrodes 158 a and 158 b. In such cases, the fieldinducing signal may be referred to as a modulation signal, and theassociated primary signal may be referred to as a modulation controlsignal. In other instances, the magnitude and/or duration of the fieldinducing signal may generate an electric field that does not result innerve modulation. In such cases, the field inducing signal may bereferred to as a sub-modulation signal.

Various characteristics of the primary control signal may be adjusted byprocessor 144 so as to cause differring responses in the implant. Forexample, characteristics of the primary control signal may be adjustedto cause various types of field inducing signals, both modulationsignals and sub-modulation signals, at electrodes 158 a and 158 b ofimplant unit 110. Adjusted characteristics may include, for example,voltage, current, frequency, pulse rate, pulse width, and signalduration. For example, in some embodiments, a modulation signal mayinclude a moderate amplitude (defined by voltage or current) andmoderate duration, while in other embodiments, a modulation signal mayinclude a higher amplitude and a shorter duration. Various amplitudesand/or durations of field-inducing signals across electrodes 158 a, 158b may result in modulation signals, and whether a field-inducing signalrises to the level of a modulation signal can depend on many factors(e.g., distance from a particular nerve to be stimulated; whether thenerve is branched; orientation of the induced electric field withrespect to the nerve; type of tissue present between the electrodes andthe nerve; etc.). For example, the modulation signal may include avoltage between about 0.5 volts and about 40 volts or electric currentbetween about 50 microamps and about 20 milliamps.

In some embodiments, the electrodes 158 a and 158 b may generate anelectric field configured to penetrate intervening tissue 111 betweenthe electrodes and one or more nerves. The intervening tissue 111 mayinclude muscle tissue, bone, connective tissue, adipose tissue, organtissue, or any combination thereof. For subjects suffering withobstructive sleep apnea, for instance, the intervening tissue mayinclude the genioglossus muscle.

As noted above, electrodes 158 a, 158 b may have various differentconfigurations, and in some embodiments, the electrodes may beconfigured to emit a unidirectional electric field (e.g., in response toan applied DC voltage signal). Electrodes 158 a, 158 b may further beconfigured such that modulation of at least one nerve in the vicinity ofthe electrodes may be accomplished when non-nerve tissue is interposedbetween the electrodes and the at least one nerve. For example, suchnon-nerve tissue may include muscle tissue, connective tissue, fat,blood vessel, mucosal membrane, etc. may interposed between theelectrodes and the nerve to be modulated. Electrodes 158 a, 158 b may beconfigured such that an electric field generated by the electrodes canpenetrate the tissue interposed between the electrodes and the at leastone nerve to be modulated. For example, in some embodiments theelectrodes may be configured to generate an electric field enablingmodulation of the at least one nerve when the tissue interposed betweenthe electrodes and the at least one nerve has a thickness of greaterthan about 1 mm. In other embodiments the electrodes may be configuredto generate an electric field enabling modulation of the at least onenerve when the tissue interposed between the electrodes and the at leastone nerve has a thickness of greater than about 5 mm. In still otherembodiments, the electrodes may be configured to generate an electricfield enabling modulation of the at least one nerve when the electrodesand the at least one nerve are spaced apart by a distance between about5 mm and 15 mm, or a distance between 0.1 mm and 25 mm.

As used herein, the term substantially unidirectional electric field mayrefer to an electric field having field lines parallel to one another,when viewed from an angle orthogonal to a plane on which the electrodesfacilitating the electric field are located. For example, the electricfield lines 220 illustrated in FIGS. 10A, 10B, and 10C are parallel toone another when viewed from above the drawing sheet on which theelectrodes 158 a, and 158 b are located. It is to be understood that,while electric field lines at the edges of electrodes 158 a, 158 b maycurve out from substantially parallel electric field lines 220, thefield generated may still be considered to be substantiallyunidirectional as a substantial portion of current passed betweenelectrodes 158 a and 158 b travels along parallel electric field lines.

The generation of electric fields configured to penetrate interveningtissue is now discussed with respect to FIGS. 10 a, 10 b, 10 c, and 11.In response to a field inducing signal, implant electrodes 158 a and 158b may be configured to generate a unidirectional electric field withfield lines extending generally in the longitudinal direction of one ormore nerves to be modulated. In some embodiments, implant electrodes 158a and 158 b may be spaced apart from one another along the longitudinaldirection of a nerve to facilitate generation of such an electric field.The unidirectional electric field may also be configured to extend in adirection substantially parallel to a longitudinal direction of at leastsome portion of the nerve to be modulated. For example, a substantiallyparallel field may include field lines that extend more in alongitudinal direction than a transverse direction compared to thenerve. Orienting the electric field in this way may facilitateelectrical current flow through a nerve or tissue, thereby increasingthe likelihood of eliciting an action potential to induce modulation.

FIG. 10 a illustrates a pair of electrodes 158 a, 158 b spaced apartfrom one another along the longitudinal direction of nerve 210 tofacilitate generation of an electric field having field lines 220substantially parallel to the longitudinal direction of nerve 210. In 10a, modulation electrodes 158 a, 158 b are illustrated as lineelectrodes, although the generation of substantially parallel electricfields may be accomplished through the use of other types of electrodes,including, for example, a series of point electrodes. Utilizing anelectric field having field lines 220 extending in a longitudinaldirection of nerve 210 may serve to reduce the amount of energy requiredto achieve neural modulation.

Second, more ion channels may be recruited by expanding the areaaffected by the voltage potential difference.

Returning to 10 a, it can be seen that, due to the electric field lines220 running in a direction substantially parallel to the longitudinaldirection of the nerve 210, a large portion of nerve 210 may encounterthe field. Thus, more ion channels from the neurons that make up nerve210 may be recruited without using a larger voltage potentialdifference. In this way, modulation of nerve 210 may be achieved with alower current and less power usage. FIG. 10 b illustrates an embodimentwherein electrodes 158 a and 158 are still spaced apart from one anotherin a longitudinal direction of at least a portion of nerve 210. Asignificant portion of nerve 210 remains inside of the electric field.FIG. 10 c illustrates a situation wherein electrodes 158 a and 158 b arespaced apart from one another in a transverse direction of nerve 210. Inthis illustration, it can be seen that a significantly smaller portionof nerve 210 will be affected by electric field lines 220.

FIG. 11 illustrates potential effects of electrode configuration on theshape of a generated electric field. The top row of electrodeconfigurations, e.g. A, B, and C, illustrates the effects on theelectric field shape when a distance between electrodes of a constantsize is adjusted. The bottom row of electrode configurations, e.g. D, E,and F illustrates the effects on the electric field shape when the sizeof electrodes of constant distance is adjusted.

In embodiments consistent with the present disclosure, modulationelectrodes 158 a, 158 b may be arranged on the surface of a muscle orother tissue, in order to modulate a nerve embedded within the muscle orother tissue. Thus, tissue may be interposed between modulationelectrodes 158 a, 158 b and a nerve to be modulated. Modulationelectrodes 158 a, 158 b may be spaced away from a nerve to be modulated.The structure and configuration of modulation electrodes 158 a, 158 bmay play an important role in determining whether modulation of a nerve,which is spaced a certain distance away from the electrodes, may beachieved.

Electrode configurations A, B, and C show that when modulationelectrodes 158 a, 158 b of a constant size are moved further apart, thedepth of the electric field facilitated by the electrodes increases. Thestrength of the electric field for a given configuration may varysignificantly depending on a location within the field. If a constantlevel of current is passed between modulation electrodes 158 a and 158b, however, the larger field area of configuration C may exhibit a loweroverall current density than the smaller field area of configuration A.A lower current density, in turn, implies a lower voltage potentialdifference between two points spaced equidistant from each other in thefield facilitated by configuration C relative to that of the fieldfacilitated by configuration A. Thus, while moving modulation electrodes158 a and 158 b farther from each other increases the depth of thefield, it also decreases the strength of the field. In order to modulatea nerve spaced away from modulation electrodes 158 a, 158 b, a distancebetween the electrodes may be selected in order to facilitate anelectric field of strength sufficient to surpass a membrane thresholdpotential of the nerve (and thereby modulate it) at the depth of thenerve. If modulation electrodes 158 a, 158 b are too close together, theelectric field may not extend deep enough into the tissue in order tomodulate a nerve located therein. If modulation electrodes 158 a, 158 bare too far apart, the electric field may be too weak to modulate thenerve at the appropriate depth.

Appropriate distances between modulation electrodes 158 a, 158 b, maydepend on an implant location and a nerve to be stimulated. For example,modulation point 901 is located at the same depth equidistant from thecenters of modulation electrodes 158 a, 158 b in each of configurationsA, B, and C. The figures illustrate that, in this example, configurationB is most likely to achieve the highest possible current density, andtherefore voltage potential, at modulation point 901. The field ofconfiguration A may not extend deeply enough, and the field ofconfiguration C may be too weak at that depth.

In some embodiments, modulation electrodes 158 a, 158 b may be spacedapart by about a distance of about 0.2 mm to 25 mm. In additionalembodiments, modulation electrodes 158 a, 158 b may be spaced apart by adistance of about 1 mm to 10 mm, or between 4 mm and 7 mm. In otherembodiments modulation electrodes 158 a, 158 b may be spaced apart bybetween approximately 6 mm and 7 mm.

Electrode configurations D, E, and F show that when modulationelectrodes 158 a, 158 b of a constant distance are changed in size, theshape of the electric field facilitated by the electrodes changes. If aconstant level of current is passed between when modulation electrodes158 a and 158 b, the smaller electrodes of configuration D mayfacilitate a deeper field than that of configurations E and F, althoughthe effect is less significant relative to changes in distance betweenthe electrodes. As noted above, the facilitated electric fields are notof uniform strength throughout, and thus the voltage potential atseemingly similar locations within each of the electric fields ofconfigurations D, E, and, F may vary considerably. Appropriate sizes ofmodulation electrodes 158 a, 158 b, may therefore depend on an implantlocation and a nerve to be stimulated.

In some embodiments, modulation electrodes 158 a, 158 b may have asurface area between approximately 0.01 mm² and 80 mm². In additionalembodiments, modulation electrodes 158 a, 158 b may have a surface areabetween approximately 0.1 mm² and 4 mm². In other embodiments modulationelectrodes 158 a, 158 b may have a surface area of between approximately0.25 mm² and 0.35 mm².

In some embodiments, modulation electrodes 158 a, 158 b may be arrangedsuch that the electrodes are exposed on a single side of carrier 161. Insuch an embodiment, an electric field is generated only on the side ofcarrier 161 with exposed electrodes. Such a configuration may serve toreduce the amount of energy required to achieve neural modulation,because the entire electric field is generated on the same side of thecarrier as the nerve, and little or no current is wasted travelingthrough tissue away from the nerve to be modulated. Such a configurationmay also serve to make the modulation more selective. That is, bygenerating an electric field on the side of the carrier where there is anerve to be modulated, nerves located in other areas of tissue (e.g. onthe other side of the carrier from the nerve to be modulated), may avoidbeing accidentally modulated.

As discussed above, the utilization of electric fields having electricalfield lines extending in a direction substantially parallel to thelongitudinal direction of a nerve to be modulated may serve to lower thepower requirements of modulation. This reduction in power requirementsmay permit the modulation of a nerve using less than 1.6 mA of current,less than 1.4 mA of current, less than 1.2 mA of current, less than 1 mAof current, less than 0.8 mA of current, less than 0.6 mA of current,less than 0.4 mA of current, and even less than 0.2 mA of current passedbetween modulation electrodes 158 a, 158 b.

Reducing the current flow required may have additional effects on theconfiguration of implant unit 110 and external unit 120. For example,the reduced current requirement may enable implant unit 110 to modulatea nerve without a requirement for a power storage unit, such as abattery or capacitor, to be implanted in conjunction with implant unit110. For example, implant unit 110 may be capable of modulating a nerveusing only the energy received via secondary antenna 152. Implant unit110 may be configured to serve as a pass through that directssubstantially all received energy to modulation electrodes 158 a and 158b for nerve modulation. Substantially all received energy may refer tothat portion of energy that is not dissipated or otherwise lost to theinternal components of implant unit 110. Finally, the reduction inrequired current may also serve to reduce the amount of energy requiredby external unit 120. External unit 120 may be configured to operatesuccessfully for an entire treatment session lasting from one to tenhours by utilizing a battery having a capacity of less than 240 mAh,less than 120 mAh, and even less than 60 mAh.

As discussed above, utilization of parallel fields may enable implantunit 110 to modulate nerves in a non-contacting fashion. Contactlessneuromodulation may increase the efficacy of an implanted implant unit110 over time compared to modulation techniques requiring contact with anerve or muscle to be modulated. Over time, implantable devices maymigrate within the body. Thus, an implantable device requiring nervecontact to initiate neural modulation may lose efficacy as the devicemoves within the body and loses contact with the nerve to be modulated.In contrast, implant unit 110, utilizing contactless modulation, maystill effectively modulate a nerve even if it moves away from, or toanother location relative to an initial implant location. Additionally,tissue growth and/or fibrosis may develop around an implantable device.This growth may serve to lessen or even eliminate the contact between adevice designed for contact modulation and a nerve to be modulated. Incontrast, implant unit 110, utilizing contactless modulation, maycontinue to effectively modulate a nerve if additional tissue formsbetween it and a nerve to be modulated.

As described above, modulation electrodes 158 a, 158 b, of implant unit110 may be configured so as to facilitate the generation of an electricfield sufficient to modulate a nerve even when a voltage signal of lowcurrent is applied to modulation electrodes 158 a, 158 b. In someembodiments consistent with the present disclosure, implant unit 110 mayhave no means of measuring the current of a voltage signal applied tomodulation electrodes 158 a, 158 b. In such an embodiment, processor 144may be configured to supply a voltage signal having a specific currentvalue, for example, less than about 1.6 mAmps, as follows. Processor 144may be configured to adjust the characteristics, for example, thevoltage, of a primary signal. Processor 144 may detect coupling betweenprimary antenna 152 and secondary antenna 162, and therefore determinethe voltage of the secondary signal induced on the secondary antenna 162by the primary signal. The voltage induced in the implant may drive acertain amount of current through the circuitry 180 of the implant tomodulation electrodes 158 a, 158 b. The amount of current driven throughthe implant unit 110 may depend on the voltage of the secondary signal,the configuration of implant circuitry 180, and the resistance betweenmodulation electrodes 158 a, 158 b. The resistance between modulationelectrodes 158 a, 158 b, may vary for physiological reasons becausetissue closes the circuit. Implant positioning, tissue composition,tissue hydration, and other physiological factors may all affect theresistance, and thus the current across the electrodes. The resistance,however, will vary within a small range, and the known factors, such asimplant circuitry 180, may dominate these small variations. Thus,processor 144 may be configured with information about a configurationof implant unit 110, modulation electrodes, 158 a, 158 b, and ranges ofvariation of tissue impedance so as to be able to adjust the primarysignal to an appropriate voltage in order to deliver the specifiedamount of current to modulation electrodes 158 a, 158 b in order tomodulate a nerve.

The circuitry 180 of implant unit 110 may also be configured to deliverto the electrodes an electrical signal having a current less than about1.6 milliamps. That is, the design of the implant circuitry 180, thevalues of the resistors, capacitors, diodes, and other electroniccomponents of implant circuitry 180 may be chosen specifically such thatwhen a primary signal on primary antenna 152 induces a secondary signalon secondary antenna 162, the voltage of the secondary signal will besufficient to drive the specified amount of current across modulationelectrodes 158 a, 158 b, in order to modulate a nerve.

Whether a field inducing signal constitutes a modulation signal(resulting in an electric field that may cause nerve modulation) or asub-modulation signal (resulting in an electric field not intended tocause nerve modulation) may ultimately be controlled by processor 144 ofexternal unit 120. For example, in certain situations, processor 144 maydetermine that nerve modulation is appropriate. Under these conditions,processor 144 may cause signal source 144 and amplifier 146 to generatea modulation control signal on primary antenna 150 (i.e., a signalhaving a magnitude and/or duration selected such that a resultingsecondary signal on secondary antenna 152 will provide a modulationsignal at implant electrodes 158 a and 158 b).

In some embodiments, processor 144 may be configured to adjust the oneor more characteristics of the primary signal so as to elicit thecondition signal from an implantable device. For example, whentransmitted to an implantable device such as implant unit 110, theprimary signal may be adjusted in order to cause a secondary signal inimplant unit 110 that, in turn, causes a primary coupled signalcomponent on primary antenna 144. Such adjustments may, for example, becalculated to cause implant unit 110 to generate a specific type ofharmonic resonance, as described further below. In other examples, aprimary signal may be adjusted by processor 144 to communicate with aprocessor associated with an implantable device, and to thereby elicit acondition signal from the processor associated with the implantabledevice in response.

In some embodiments, a modulation signal resulting in neural stimulationmay be provided by electrodes 158 a and 158 b in response to one or moreelectrical signals (e.g. signals having various voltage levels, currentlevels, or durations) supplied by circuitry 180. Such stimulation mayresult even when each supplied electrical signal has a current of lessthan about 1 milliamp. In such embodiments, electrodes 158 a and 158 bmay be configured to emit an electric field such that at least a portionof the field lines extend along a length of the nerve such that thedelivery of the electrical signal of less than about 1.6 milliampscauses stimulation of the nerve. Circuitry 180 (including variouscapacitor values, diode activation potentials, etc.) may be configuredto deliver a substantial portion of the energy received from externalunit 120 to the subject within about 1 second or less of receiving theenergy.

As discussed above, implant unit 110 may be secured to the surface ofnon-nerve tissue. One or more of muscle tissue, connective tissue, fat,blood vessel, and mucosal membrane may be interposed between theelectrodes and the nerve. The electrodes may be configured to generatean electric field sufficient to stimulate the underlying nerve with lessthan 1.6 milliamps of current.

Processor 144 may be configured to limit an amount of energy transferredfrom external unit 120 to implant unit 110. For example, in someembodiments, implant unit 110 may be associated with a threshold energylimit that may take into account multiple factors associated with thepatient and/or the implant. For example, in some cases, certain nervesof a patient should receive no more than a predetermined maximum amountof energy to minimize the risk of damaging the nerves and/or surroundingtissue. Additionally, circuitry 180 of implant unit 110 may includecomponents having a maximum operating voltage or power level that maycontribute to a practical threshold energy limit of implant unit 110.For example, components including diodes may be included in implant unit110 or in external unit 120 to limit power transferred from the externalunit 120 to the implant unit 110. In some embodiments, diode 156 mayfunction to limit or substantially restrict the power level received bythe patient. Processor 144 may be configured to account for suchlimitations when setting the magnitude and/or duration of a primarysignal to be applied to primary antenna 150. As described above, thisinformation may be received by processor 144 via a condition signal fromthe implantable device indicative of a maximum power limit.

In addition to determining an upper limit of power that may be deliveredto implant unit 110, processor 144 may also determine a lower powerthreshold based, at least in part, on an efficacy of the deliveredpower. The lower power threshold may be computed based on a minimumamount of power that enables nerve modulation (e.g., signals havingpower levels above the lower power threshold may constitute modulationsignals while signals having power levels below the lower powerthreshold may constitute sub-modulation signals). As described above,this information may be received by processor 144 via a condition signalfrom the implantable device indicative of a minimum efficacy threshold.

A lower power threshold may also be measured or provided in alternativeways. For example, appropriate circuitry or sensors in the implant unit110 may measure a lower power threshold. A lower power threshold may becomputed or sensed by an additional external device, and subsequentlyprogrammed into processor 144, or programmed into implant unit 110.Alternatively, implant unit 110 may be constructed with circuitry 180specifically chosen to generate signals at the electrodes of at leastthe lower power threshold. In still another embodiment, an antenna ofexternal unit 120 may be adjusted to accommodate or produce a signalcorresponding to a specific lower power threshold. The lower powerthreshold may vary from patient to patient, and may take into accountmultiple factors, such as, for example, modulation characteristics of aparticular patient's nerve fibers, a distance between implant unit 110and external unit 120 after implantation, and the size and configurationof implant unit components (e.g., antenna and implant electrodes), etc.

Processor 144 may also be configured to cause application ofsub-modulation control signals to primary antenna 150. Suchsub-modulation control signals may include an amplitude and/or durationthat result in a sub-modulation signal at electrodes 158 a, 158 b. Whilesuch sub-modulation control signals may not result in nerve modulation,such sub-modulation control signals may enable feedback-based control ofthe nerve modulation system. That is, in some embodiments, processor 144may be configured to cause application of a sub-modulation controlsignal to primary antenna 150. This signal may induce a secondary signalon secondary antenna 152, which, in turn, induces a primary coupledsignal component on primary antenna 150.

To analyze the primary coupled signal component induced on primaryantenna 150, external unit 120 may include a feedback circuit 148 (e.g.,a signal analyzer or detector, etc.), which may be placed in direct orindirect communication with primary antenna 150 and processor 144.Sub-modulation control signals may be applied to primary antenna 150 atany desired periodicity. In some embodiments, the sub-modulation controlsignals may be applied to primary antenna 150 at a rate of one everyfive seconds (or longer). In other embodiments, the sub-modulationcontrol signals may be applied more frequently (e.g., once every twoseconds, once per second, once per millisecond, once per nanosecond, ormultiple times per second). Further, it should be noted that feedbackmay also be received upon application of modulation control signals toprimary antenna 150 (i.e., those that result in nerve modulation), assuch modulation control signals may also result in generation of aprimary coupled signal component on primary antenna 150.

The primary coupled signal component may be fed to processor 144 byfeedback circuit 148 and may be used as a basis for determining a degreeof coupling between primary antenna 150 and secondary antenna 152.Measuring the degree of coupling may enable determination of theefficacy of the energy transfer between two antennas. Processor 144 mayalso use the determined degree of coupling in regulating delivery ofpower to implant unit 110.

In some embodiments consistent with the present disclosure, processor144 may be configured to adjust the one or more characteristics of theprimary signal based on the condition signal from the implantabledevice. For example, as described in greater detail below, a conditionsignal indicative of coupling between primary antenna 150 and secondaryantenna 152 may be used by the processor to determine a suitableresponse. In other examples, a processor associated with an implantabledevice may generate and cause the transmission of a condition signalcontaining information which the at least one processor 144 may use toadjust the characteristics of the primary signal.

Processor 144 may be configured with any suitable logic for determininghow to regulate power transfer to implant unit 110 based on thedetermined degree of coupling. Processor 144 may, for example, utilize abaseline coupling range. Presumably, while the patient is awake, thetongue is not blocking the patient's airway and moves with the patient'sbreathing in a natural range, where coupling between primary antenna 150and secondary antenna 152 may be within a baseline coupling range. Abaseline coupling range may encompass a maximum coupling between primaryantenna 150 and secondary antenna 152. A baseline coupling range mayalso encompass a range that does not include a maximum coupling levelbetween primary antenna 150 and secondary antenna 152. Processor 144 maybe configured to determine the baseline coupling range based on acommand from a user, such as the press of a button on the patch or thepress of a button on a suitable remote device. Alternatively oradditionally, processor 144 may be configured to automatically determinethe baseline coupling range when external unit 120 is placed such thatprimary antenna 150 and secondary antenna 152 are within range of eachother. In such an embodiment, when processor 144 detects any degree ofcoupling between primary antenna 150 and secondary antenna 152, it mayimmediately begin tracking a baseline coupling range. Processor 144 maythen determine a baseline coupling range when it detects that the onlymovement between primary antenna 150 and secondary antenna 152 is causedby a patient's natural breathing rhythm (i.e. the patient has securedthe external unit to an appropriate location on their body).Additionally, processor 144 may be configured such that it measurescoupling between the primary antenna 150 and the secondary antenna 152for a specified period of time after activation in order to determine abaseline coupling range, such as 1 minute, 5 minutes, 10 minutes, etc.

A condition signal, for example, a primary coupled signal component, mayindicate that a degree of coupling has changed from a baseline couplingrange, processor 144 may determine that secondary antenna 152 has movedwith respect to primary antenna 150 (either in coaxial offset, lateraloffset, or angular offset, or any combination). Such movement, forexample, may be associated with a movement of the implant unit 110, andthe tissue that it is associated with based on its implant location. Thecondition signal, therefore, may be indicative of movement and/orlocation of the implantable device. In such situations, processor 144may determine that modulation of a nerve in the patient's body isappropriate. In some embodiments, a condition signal indicative of apredetermined amount of movement of the implantable device may triggerthe transmission of the primary signal. For example, in response to anindication of a change in coupling, processor 144, in some embodiments,may cause application of a modulation control signal to primary antenna150 in order to generate a modulation signal at implant electrodes 158a, 158 b, e.g., to cause modulation of a nerve of the patient.

In an embodiment for the treatment of OSA, movement of an implant unit110 may be indicative of tongue movement associated with sleepdisordered breathing, such as the onset of a sleep apnea event or asleep apnea precursor. An amount of tongue movement may be indicative ofthe severity of the sleep disordered breathing. The onset of a sleepapnea event of sleep apnea precursor may require the stimulation of thegenioglossus muscle of the patient to relieve or avert the event. Suchstimulation may result in contraction of the muscle and movement of thepatient's tongue away from the patient's airway.

In embodiments for the treatment of head pain, including migraines,processor 144 may be configured to generate a modulation control signalbased on a signal from a user, for example, or a detected level ofneural activity in a sensory neuron (e.g. the greater occipital nerve ortrigeminal nerve) associated with head pain. A modulation control signalgenerated by the processor and applied to the primary antenna 150 maygenerate a modulation signal at implant electrodes 158 a, 158 b, e.g.,to cause inhibition or blocking (i.e. a down modulation) of a sensorynerve of the patient. Such inhibition or blocking may decrease oreliminate the sensation of pain for the patient.

In embodiments for the treatment of hypertension, processor 144 may beconfigured to generate a modulation control signal based on, forexample, pre-programmed instructions and/or signals from an implantindicative of blood pressure. A modulation control signal generated bythe processor and applied to the primary antenna 150 may generate amodulation signal at implant electrodes 158 a, 158 b, e.g., to causeeither inhibition or stimulation of nerve of a patient, depending on therequirements. For example, a neuromodulator placed in a carotid arteryor jugular vein (i.e. in the vicinity of a carotid baroreceptor), mayreceive a modulation control signal tailored to induce a stimulationsignal at the electrodes, thereby causing the glossopharyngeal nerveassociated with the carotid baroreceptors to fire at an increased ratein order to signal the brain to lower blood pressure. Similar modulationof the glossopharyngeal nerve may be achieved with a neuromodulatorimplanted in a subcutaneous location in a patient's neck or behind apatient's ear. A neuromodulator place in a renal artery may receive amodulation control signal tailored to cause an inhibiting or blockingsignal (i.e. a down modulation) at the electrodes, thereby inhibiting asignal to raise blood pressure carried from the renal nerves to thekidneys.

Modulation control signals may include stimulation control signals, andsub-modulation control signals may include sub-stimulation controlsignals. Stimulation control signals may have any amplitude, pulseduration, or frequency combination that results in a stimulation signalat electrodes 158 a, 158 b. In some embodiments (e.g., at a frequency ofbetween about 6.5-13.6 MHz), stimulation control signals may include apulse duration of greater than about 50 microseconds and/or an amplitudeof approximately 0.5 amps, or between 0.1 amps and 1 amp, or between0.05 amps and 3 amps. Sub-stimulation control signals may have a pulseduration less than about 500, or less than about 200 nanoseconds and/oran amplitude less than about 1 amp, 0.5 amps, 0.1 amps, 0.05 amps, or0.01 amps. Of course, these values are meant to provide a generalreference only, as various combinations of values higher than or lowerthan the exemplary guidelines provided may or may not result in nervestimulation.

In some embodiments, stimulation control signals may include a pulsetrain, wherein each pulse includes a plurality of sub-pulses. Naturallyfunctioning neurons function by transmitting action potentials alongtheir length. Structurally, neurons include multiple ion channels alongtheir length that serve to maintain a voltage potential gradient acrossa plasma membrane between the interior and exterior of the neuron. Ionchannels operate by maintaining an appropriate balance betweenpositively charged sodium ions on one side of the plasma membrane andnegatively charged potassium ions on the other side of the plasmamembrane. A sufficiently high voltage potential difference created nearan ion channel may exceed a membrane threshold potential of the ionchannel. The ion channel may then be induced to activate, pumping thesodium and potassium ions across the plasma membrane to switch places inthe vicinity of the activated ion channel. This, in turn, further altersthe potential difference in the vicinity of the ion channel, which mayserve to activate a neighboring ion channel. The cascading activation ofadjacent ion channels may serve to propagate an action potential alongthe length of the neuron. Further, the activation of an ion channel inan individual neuron may induce the activation of ion channels inneighboring neurons that, bundled together, form nerve tissue. Theactivation of a single ion channel in a single neuron, however, may notbe sufficient to induce the cascading activation of neighboring ionchannels necessary to permit the propagation of an action potential.Thus, the more ion channels in a locality that may be recruited by aninitial potential difference, caused through natural means such as theaction of nerve endings or through artificial means, such as theapplication of electric fields, the more likely the propagation of anaction potential may be. The process of artificially inducing thepropagation of action potentials along the length of a nerve may bereferred to as stimulation or up modulation.

Neurons may also be prevented from functioning naturally throughconstant or substantially constant application of a voltage potentialdifference. After activation, each ion channel experiences a refractoryperiod, during which it “resets” the sodium and potassium concentrationsacross the plasma membrane back to an initial state. Resetting thesodium and potassium concentrations causes the membrane thresholdpotential to return to an initial state. Until the ion channel restoresan appropriate concentration of sodium and potassium across the plasmamembrane, the membrane threshold potential will remain elevated, thusrequiring a higher voltage potential to cause activation of the ionchannel. If the membrane threshold potential is maintained at a highenough level, action potentials propagated by neighboring ion channelsmay not create a large enough voltage potential difference to surpassthe membrane threshold potential and activate the ion channel. Thus, bymaintaining a sufficient voltage potential difference in the vicinity ofa particular ion channel, that ion channel may serve to block furthersignal transmission. The membrane threshold potential may also be raisedwithout eliciting an initial activation of the ion channel. If an ionchannel (or a plurality of ion channels) are subjected to an elevatedvoltage potential difference that is not high enough to surpass themembrane threshold potential, it may serve to raise the membranethreshold potential over time, thus having a similar effect to an ionchannel that has not been permitted to properly restore ionconcentrations. Thus, an ion channel may be recruited as a block withoutactually causing an initial action potential to propagate. This methodmay be valuable, for example, in pain management, where the propagationof pain signals is undesired. As described above with respect tostimulation, the larger the number of ion channels in a locality thatmay be recruited to serve as blocks, the more likely the chance that anaction potential propagating along the length of the nerve will beblocked by the recruited ion channels, rather than traveling throughneighboring, unblocked channels.

The number of ion channels recruited by a voltage potential differencemay be increased in at least two ways. First, more ion channels may berecruited by utilizing a larger voltage potential difference in a localarea. Second, more ion channels may be recruited by expanding the areaaffected by the voltage potential difference. In some embodiments, theat least one processor may be configured to cause transmission of aprimary signal from the primary antenna to an implantable device duringa treatment session of at least three hours in duration. During such atreatment such, the primary signal may be generated using power suppliedby power source associated with the processor, such as a battery. Theprimary signal during such a treatment session may include a pulsetrain, as illustrated, for example, in FIG. 10.

FIG. 17 depicts the composition of an exemplary modulation pulse train.Such a pulse train 1010 may include a plurality of modulation pulses1020, wherein each modulation pulse 1020 may include a plurality ofmodulation sub-pulses 1030. FIG. 17 is exemplary only, at a scaleappropriate for illustration, and is not intended to encompass all ofthe various possible embodiments of a modulation pulse train, discussedin greater detail below. An alternating current signal (e.g., at afrequency of between about 6.5-13.6 MHz) may be used to generate a pulsetrain 1010, as follows. A sub-pulse 1030 may have a pulse duration ofbetween 50-250 microseconds, or a pulse duration of between 1microsecond and 2 milliseconds, during which an alternating currentsignal is turned on. For example, a 200 microsecond sub-pulse 1030 of a10 MHz alternating current signal will include approximately 2000periods. Each modulation pulse 1020 may, in turn, have a pulse duration1040 of between 100 and 500 milliseconds, during which sub-pulses 1030occur at a frequency of between 25 and 100 Hz. Thus, a modulation pulse1020 may include between about 2.5 and 50 modulation sub-pulses 1030. Insome embodiments, a modulation 1020 pulse may include between about 5and 15 modulation sub-pulses 1030. For example, a 200 millisecondmodulation pulse 1020 of 50 Hz modulation sub-pulses 1030 will includeapproximately 10 modulation sub-pulses 1030. Finally, in a modulationpulse train 1010, each modulation pulse 1020 may be separated from thenext by a temporal spacing 1050 of between 0.2 and 2 seconds. Forexample, in a pulse train 1010 of 200 millisecond pulse duration 1040modulation pulses 1020, each separated by a 1.3 second temporal spacing1050 from the next, a new modulation pulse 1020 will occur every 1.5seconds. The frequency of modulation pulses 1020 may also be timed to inaccordance with physiological events of the subject. For example,modulation pulses 1020 may occur at a frequency chosen from among anymultiple of a breathing frequency, such as four, eight, or sixteen. Inanother example, modulation pulses 1020 may be temporally spaced so asnot to permit a complete relaxation of a muscle after causing a muscularcontraction. The pulse duration 1040 of modulation pulses 1020 and thetemporal spacing 1050 between modulation pulses 1020 in a pulse train1010 may be maintained for a majority of the modulation pulses 1020, ormay be varied over the course of a treatment session according to asubjects need. Such variations may also be implemented for themodulation sub-pulse duration and temporal spacing.

Pulse train 1010 depicts a primary signal pulse train, as generated byexternal unit 120. In some embodiments, the primary signal may result ina secondary signal on the secondary antenna 152 of implant unit 110.This signal may be converted to a direct current signal for delivery tomodulation electrodes 158 a, 158 b. In this situation, the generation ofmodulation sub-pulse 1030 may result in the generation and delivery of asquare wave of a similar duration as modulation sub-pulse 1030 tomodulation electrodes 158 a, 158 b.

In an embodiment for the treatment of sleep disordered breathing,modulation pulses 1020 and modulation sub-pulses 1030 may includestimulation pulses and stimulation sub-pulses adapted to cause neuralstimulation. A pulse train 1010 of this embodiment may be utilized, forexample, to provide ongoing stimulation during a treatment session.Ongoing stimulation during a treatment session may include transmissionof the pulse train for at least 70%, at least 80%, at least 90%, and atleast 99% of the treatment session. In the context of sleep disorderedbreathing, a treatment session may be a period of time during which asubject is asleep and in need of treatment to prevent sleep disorderedbreathing. Such a treatment session may last anywhere from about threeto ten hours. A treatment session may include as few as approximately4,000 and as many as approximately 120,000 modulation pulses 1020. Insome embodiments, a pulse train 1010 may include at least 5,000, atleast 10,000, and at least 100,000 modulation pulses 1020. In thecontext of other conditions to which neural modulators of the presentdisclosure are applied, a treatment session may be of varying lengthaccording to the duration of the treated condition.

Exemplary treatment regimes for head pain management and hypertensiontherapy may differ from a sleep disordered breathing treatment regime.For example, in an exemplary head pain management treatment regime,temporal spacing 1050 may be reduced to less than 3 milliseconds, lessthan 2 milliseconds, less than 1 millisecond, or even eliminatedaltogether. Furthermore, the spacing between sub-pulses 1030 may also bereduced to less than 3 milliseconds, less than 2 milliseconds, less than1 millisecond, or even eliminated altogether. The amplitude ofsub-pulses 1030 and pulses 1020 may be reduced to a level sufficient torecruit ion channels as blocks but not elicit an action potential. Aduration of sub-pulses 1030 may also be reduced to between about 50microseconds and 100 microseconds. Thus, pulse train 1010 may be adaptedto maintain a plurality of ion channels as blocks that will not permitthe propagation of action potentials along the nerve. When such a pulsetrain 1010 is applied to a nerve that typically carries a pain signal,such as a greater occipital nerve, lesser occipital nerve, or trigeminalnerve, the amount of pain experienced by a subject may be reduced.Temporal spacing 1050 and spacing between sub-pulses 1030 may be reducedsuch that the recruited ion channels do not have enough time to restoretheir ion concentrations in preparation for activation. Thus, aneffective neural block may still be created without a constantmodulation. A pulse train 1010 where temporal spacing 1050 and spacingbetween sub-pulses 1030 is not entirely eliminated may be valuable forconserving power.

Exemplary hypertension therapy regimes may vary based on implantlocation. For example, an exemplary hypertension therapy regime forapplying neural modulation to a renal nerve may be similar to a headpain management treatment regime, as the objective is to reduce oreliminate the signals sent along the renal nerve. Such treatment may bevaluable because the active propagation of signals along the renal nervemay indicate a need to increase blood pressure.

In contrast, active propagation of signals from the carotidbaroreceptor, which travel along the glossopharyngeal nerve, mayindicate a need to reduce blood pressure. Thus, an exemplaryhypertension therapy regime for applying neural modulation to a carotidbaroreceptor or glossopharyngeal nerve may involve stimulation pulses topropagate action potentials. Functioning normally, signals propagatingfrom the carotid baroreceptors along the glossopharyngeal nerve indicatea need to reduce blood pressure through an increased frequency ofsignals. Thus, an exemplary pulse train 1010 for treatment ofhypertension by applying neural modulation to a carotid baroreceptor orglossopharyngeal nerve may involve a reduction in pulse duration 1040,temporal spacing 1050, and spacing between sub-pulses 1030, therebyincreasing the frequency of pulses 1020 and sub-pulses 1030. Sub-pulseduration 1030 may be reduced because it is only required to send a briefaction potential, or spike, along the nerve, (e.g. rather than asustained signal to cause a muscle to continuously contract). Temporalspacing 1050 may be eliminated or reduced to increase the frequency ofspikes so as to indicate to the brain a need for blood pressurereduction. Sub-pulse duration 1030 may be reduced to between about 100microseconds and 50 microseconds. Spacing between sub-pulses 1030 may bealtered such that sub-pulses 1030 occur at a rate of between about 2 to100 Hz. During a hypertension treatment session, a pulse train 1010, asdescribed above, may be delivered for approximately thirty seconds everyminute, every five minutes, every ten minutes, every thirty minutes, oreven every hour.

Processor 144 may be configured to determine a degree of couplingbetween primary antenna 150 and secondary antenna 152 by monitoring oneor more aspects of the primary coupled signal component received throughfeedback circuit 148. In some embodiments, processor 144 may determine adegree of coupling between primary antenna 150 and secondary antenna 152by monitoring a voltage level associated with the primary coupled signalcomponent, a current level, or any other attribute that may depend onthe degree of coupling between primary antenna 150 and secondary antenna152. For example, in response to periodic sub-modulation signals appliedto primary antenna 150, processor 144 may determine a baseline voltagelevel or current level associated with the primary coupled signalcomponent. This baseline voltage level, for example, may be associatedwith a range of movement of the patient's tongue when a sleep apneaevent or its precursor is not occurring, e.g. during normal breathing.As the patient's tongue moves toward a position associated with a sleepapnea event, moves in a manner consistent with a precursor of sleepapnea, or moves in any other manner (e.g., vibration, etc.), thecoaxial, lateral, or angular offset between primary antenna 150 andsecondary antenna 152 may change. As a result, the degree of couplingbetween primary antenna 150 and secondary antenna 152 may change, andthe voltage level or current level of the primary coupled signalcomponent on primary antenna 150 may also change. Processor 144 may beconfigured to recognize a sleep apnea event or its precursor when avoltage level, current level, or other electrical characteristicassociated with the primary coupled signal component changes by apredetermined amount or reaches a predetermined absolute value. Such apredetermined amount of change in the primary coupled signal componentmay be associated with a predetermined amount of movement of theimplantable device.

FIG. 7 provides a graph that illustrates this principle in more detail.For a two-coil system where one coil receives a radio frequency (RF)drive signal, graph 200 plots a rate of change in induced current in thereceiving coil as a function of coaxial distance between the coils. Forvarious coil diameters and initial displacements, graph 200 illustratesthe sensitivity of the induced current to further displacement betweenthe coils, moving them either closer together or further apart. It alsoindicates that, overall, the induced current in the secondary coil willdecrease as the secondary coil is moved away from the primary, drivecoil, i.e. the rate of change of induced current, in mA/mm, isconsistently negative. The sensitivity of the induced current to furtherdisplacement between the coils varies with distance. For example, at aseparation distance of 10 mm, the rate of change in current as afunction of additional displacement in a 14 mm coil is approximately −6mA/mm. If the displacement of the coils is approximately 22 mm, the rateof change in the induced current in response to additional displacementis approximately −11 mA/mm, which corresponds to a local maximum in therate of change of the induced current. Increasing the separationdistance beyond 22 mm continues to result in a decline in the inducedcurrent in the secondary coil, but the rate of change decreases. Forexample, at a separation distance of about 30 mm, the 14 mm coilexperiences a rate of change in the induced current in response toadditional displacement of about −8 mA/mm. With this type ofinformation, processor 144 may be able to determine a particular degreeof coupling between primary antenna 150 and secondary antenna 152, atany given time, by observing the magnitude and/or rate of change in themagnitude of the current associated with the primary coupled signalcomponent on primary antenna 150.

Processor 144 may be configured to determine a degree of couplingbetween primary antenna 150 and secondary antenna 152 by monitoringother aspects of the primary coupled signal component. For example, insome embodiments, the non-linear behavior of circuitry 180 in implantunit 110 may be monitored to determine a degree of coupling. Forexample, the presence, absence, magnitude, reduction and/or onset ofharmonic components in the primary coupled signal component on primaryantenna 150 may reflect the behavior of circuitry 180 in response tovarious control signals (either sub-modulation or modulation controlsignals) and, therefore, may be used to determine a degree of couplingbetween primary antenna 150 and secondary antenna 152.

As shown in FIG. 6, circuitry 180 in implant unit 110 may constitute anon-linear circuit due, for example, to the presence of non-linearcircuit components, such as diode 156. Such non-linear circuitcomponents may induce non-linear voltage responses under certainoperation conditions. Non-linear operation conditions may be inducedwhen the voltage potential across diode 156 exceeds the activationthreshold for diode 156. Thus, when implant circuitry 180 is excited ata particular frequency, this circuit may oscillate (or harmonicallyresonate) at multiple frequencies. The harmonic resonance may besymmetric or asymmetric. Spectrum analysis of the secondary signal onsecondary antenna 152, therefore, may reveal one or more oscillations,called harmonics, that appear at certain multiples of the excitationfrequency. Through coupling of primary antenna 150 and secondary antenna152, any harmonics produced by implant circuitry 180 and appearing onsecondary antenna 152 may also appear in the primary coupled signalcomponent present on primary antenna 150.

In certain embodiments, circuitry 180 may include additional circuitcomponents that alter the characteristics of the harmonics generated incircuitry 180 above a certain transition point. Monitoring how thesenon-linear harmonics behave above and below the transition point mayenable a determination of a degree of coupling between primary antenna150 and secondary antenna 152. For example, as shown in FIG. 6,circuitry 180 may include a harmonics modifier circuit 154, which mayinclude any electrical components that non-linearly alter the harmonicsgenerated in circuitry 180. In some embodiments, harmonics modifiercircuit 154 may include a pair of Zener diodes. Below a certain voltagelevel, these Zener diodes remain forward biased such that no currentwill flow through either diode. Above the breakdown voltage of the Zenerdiodes, however, these devices become conductive in the reversed biaseddirection and will allow current to flow through harmonics modifiercircuit 154. Once the Zener diodes become conductive, they begin toaffect the oscillatory behavior of circuitry 180, and, as a result,certain harmonic oscillation frequencies may be affected (e.g., reducedin magnitude).

FIGS. 8 and 9 illustrate this effect. For example, FIG. 8 illustrates agraph 300 a that shows the oscillatory behavior of circuitry 180 atseveral amplitudes ranging from about 10 nano amps to about 20microamps. As shown, the primary excitation frequency occurs at about6.7 MHz and harmonics appear both at even and odd multiples of theprimary excitation frequency. For example, even multiples appear attwice the excitation frequency (peak 302 a), four times the excitationfrequency (peak 304 a) and six times the excitation frequency (peak 306a). As the amplitude of the excitation signal rises between 10 nanoampsand 40 microamps, the amplitude of peaks 302 a, 304 a, and 306 a allincrease.

FIG. 9 illustrates the effect on the even harmonic response of circuitry180 caused by harmonics modifier circuit 154. FIG. 9 illustrates a graph300 b that shows the oscillatory behavior of circuitry 180 at severalamplitudes ranging from about 30 microamps to about 100 microamps. As inFIG. 8, FIG. 9 shows a primary excitation frequency at about 6.7 MHz andsecond, fourth, and sixth order harmonics (peaks 302 b, 304 b, and 306b, respectively) appearing at even multiples of the excitationfrequency. As the amplitude of the excitation signal rises, however,between about 30 microamps to about 100 microamps, the amplitudes ofpeaks 302 b, 304 b, and 306 b do not continuously increase. Rather, theamplitude of the second order harmonics decreases rapidly above acertain transition level (e.g., about 80 microamps in FIG. 8). Thistransition level corresponds to the level at which the Zener diodesbecome conductive in the reverse biased direction and begin to affectthe oscillatory behavior of circuitry 180.

Monitoring the level at which this transition occurs may enable adetermination of a degree of coupling between primary antenna 150 andsecondary antenna 152. For example, in some embodiments, a patient mayattach external unit 120 over an area of the skin under which implantunit 110 resides. Processor 144 can proceed to cause a series ofsub-modulation control signals to be applied to primary antenna 150,which in turn cause secondary signals on secondary antenna 152. Thesesub-modulation control signals may progress over a sweep or scan ofvarious signal amplitude levels. By monitoring the resulting primarycoupled signal component on primary antenna 150 (generated throughcoupling with the secondary signal on secondary antenna 152), processor144 can determine the amplitude of primary signal (whether asub-modulation control signal or other signal) that results in asecondary signal of sufficient magnitude to activate harmonics modifiercircuit 154. That is, from a location remote from implant unit 110,processor 144 can monitor the amplitude of the second, fourth, or sixthorder harmonics and determine the amplitude of the primary signal atwhich the amplitude of any of the even harmonics drops. FIGS. 8 and 9illustrate the principles of detecting coupling through the measurementof non-linear harmonics. These Figures illustrate data based around a6.7 MHz excitation frequency. These principles, however, are not limitedto the 6.7 MHz excitation frequency illustrated, and may be used with aprimary signal of any suitable frequency.

In embodiments utilizing non-linear harmonics, the determined amplitudeof the primary signal corresponding to the transition level of the Zenerdiodes (which may be referred to as a primary signal transitionamplitude) may establish the baseline coupling range when the patientattaches external unit 120 to the skin. Thus, the initially determinedprimary signal transition amplitude may be fairly representative of anon-sleep apnea condition and may be used by processor 144 as a baselinein determining a degree of coupling between primary antenna 150 andsecondary antenna 152. Optionally, processor 144 may also be configuredto monitor the primary signal transition amplitude over a series ofscans and select the minimum value as a baseline, as the minimum valuemay correspond to a condition of maximum coupling between primaryantenna 150 and secondary antenna 152 during normal breathingconditions.

As the patient wears external unit 120, processor 144 may periodicallyscan over a range of primary signal amplitudes to determine a currentvalue of the primary signal transition amplitude. In some embodiments,the range of amplitudes that processor 144 selects for the scan may bebased on (e.g., near) the level of the baseline primary signaltransition amplitude. If a periodic scan results in determination of aprimary signal transition amplitude different from the baseline primarysignal transition amplitude, processor 144 may determine that there hasbeen a change from the baseline initial conditions. For example, in someembodiments, an increase in the primary signal transition amplitude overthe baseline value may indicate that there has been a reduction in thedegree of coupling between primary antenna 150 and secondary antenna 152(e.g., because the implant has moved or an internal state of the implanthas changed).

In addition to determining whether a change in the degree of couplinghas occurred, processor 144 may also be configured to determine aspecific degree of coupling based on an observed primary signaltransition amplitude. For example, in some embodiments, processor 144may have access to a lookup table or a memory storing data thatcorrelates various primary signal transition amplitudes with distances(or any other quantity indicative of a degree of coupling which may, forexample, be indicative of movement of the tongue) between primaryantenna 150 and secondary antenna 152. In other embodiments, processor144 may be configured to calculate a degree of coupling based onperformance characteristics of known circuit components.

By periodically determining a degree of coupling value, processor 144may be configured to determine, in situ, appropriate parameter valuesfor the modulation control signal that will ultimately result in nervemodulation. For example, by determining the degree of coupling betweenprimary antenna 150 and secondary antenna 152, processor 144 may beconfigured to select characteristics of the modulation control signal(e.g., amplitude, pulse duration, frequency, etc.) that may provide amodulation signal at electrodes 158 a, 158 b in proportion to orotherwise related to the determined degree of coupling. In someembodiments, processor 144 may access a lookup table or other datastored in a memory correlating modulation control signal parametervalues with degree of coupling. In this way, processor 144 may adjustthe applied modulation control signal in response to an observed degreeof coupling.

Additionally or alternatively, processor 144 may be configured todetermine the degree of coupling between primary antenna 150 andsecondary antenna 152 during modulation. The tongue, or other structureon or near which the implant is located, and thus implant unit 110, maymove as a result of modulation. Thus, the degree of coupling may changeduring modulation. Processor 144 may be configured to determine thedegree of coupling as it changes during modulation, in order todynamically adjust characteristics of the modulation control signalaccording to the changing degree of coupling. This adjustment may permitprocessor 144 to cause implant unit 110 to provide an appropriatemodulation signal at electrodes 158 a, 158 b throughout a modulationevent. For example, processor 144 may alter the primary signal inaccordance with the changing degree of coupling in order to maintain aconstant modulation signal, or to cause the modulation signal to bereduced in a controlled manner according to patient needs.

More particularly, the response of processor 144 may be correlated tothe determined degree of coupling. In situations where processor 144determines that the degree of coupling between primary antenna 150 andsecondary antenna has fallen only slightly below a predeterminedcoupling threshold (e.g, during snoring or during a small vibration ofthe tongue or other sleep apnea event precursor), processor 144 maydetermine that only a small response is necessary. Thus, processor 144may select modulation control signal parameters that will result in arelatively small response (e.g., a short stimulation of a nerve, smallmuscle contraction, etc.). Where, however, processor 144 determines thatthe degree of coupling has fallen substantially below the predeterminedcoupling threshold (e.g., where the tongue has moved enough to cause asleep apnea event), processor 144 may determine that a larger responseis required. As a result, processor 144 may select modulation controlsignal parameters that will result in a larger response. In someembodiments, only enough power may be transmitted to implant unit 110 tocause the desired level of response. In other words, processor 144 maybe configured to cause a metered response based on the determined degreeof coupling between primary antenna 150 and secondary antenna 152. Asthe determined degree of coupling decreases, processor 144 may causetransfer of power in increasing amounts. Such an approach may preservebattery ife in the external unit 120, may protect circuitry 170 andcircuitry 180, may increase effectiveness in addressing the type ofdetected condition (e.g., sleep apnea, snoring, tongue movement, etc.),and may be more comfortable for the patient.

In some embodiments, processor 144 may employ an iterative process inorder to select modulation control signal parameters that result in adesired response level. For example, upon determining that a modulationcontrol signal should be generated, processor 144 may cause generationof an initial modulation control signal based on a set of predeterminedparameter values. If feedback from feedback circuit 148 indicates that anerve has been modulated (e.g, if an increase in a degree of coupling isobserved), then processor 144 may return to a monitoring mode by issuingsub-modulation control signals. If, on the other hand, the feedbacksuggests that the intended nerve modulation did not occur as a result ofthe intended modulation control signal or that modulation of the nerveoccurred but only partially provided the desired result (e.g, movementof the tongue only partially away from the airway), processor 144 maychange one or more parameter values associated with the modulationcontrol signal (e.g., the amplitude, pulse duration, etc.).

Where no nerve modulation occurred, processor 144 may increase one ormore parameters of the modulation control signal periodically until thefeedback indicates that nerve modulation has occurred. Where nervemodulation occurred, but did not produce the desired result, processor144 may re-evaluate the degree of coupling between primary antenna 150and secondary antenna 152 and select new parameters for the modulationcontrol signal targeted toward achieving a desired result. For example,where stimulation of a nerve causes the tongue to move only partiallyaway from the patient's airway, additional stimulation may be desired.Because the tongue has moved away from the airway, however, implant unit110 may be closer to external unit 120 and, therefore, the degree ofcoupling may have increased. As a result, to move the tongue a remainingdistance to a desired location may require transfer to implant unit 110of a smaller amount of power than what was supplied prior to the laststimulation-induced movement of the tongue. Thus, based on a newlydetermined degree of coupling, processor 144 can select new parametersfor the stimulation control signal aimed at moving the tongue theremaining distance to the desired location.

In one mode of operation, processor 144 may be configured to sweep overa range of parameter values until nerve modulation is achieved. Forexample, in circumstances where an applied sub-modulation control signalresults in feedback indicating that nerve modulation is appropriate,processor 144 may use the last applied sub-modulation control signal asa starting point for generation of the modulation control signal. Theamplitude and/or pulse duration (or other parameters) associated withthe final applied to primary antenna 150 may be iteratively increased bypredetermined amounts and at a predetermined rate until the feedbackindicates that nerve modulation has occurred.

Processor 144 may be configured to determine or derive variousphysiologic data based on the determined degree of coupling betweenprimary antenna 150 and secondary antenna 152. For example, in someembodiments the degree of coupling may indicate a distance betweenexternal unit 120 and implant unit 110, which processor 144 may use todetermine a position of external unit 120 or a relative position of apatient's tongue. Monitoring the degree of coupling can also providesuch physiologic data as whether a patient's tongue is moving orvibrating (e.g, whether the patient is snoring), by how much the tongueis moving or vibrating, the direction of motion of the tongue, the rateof motion of the tongue, etc. Accordingly, processor 144 may beconfigured to receive a signal from implant unit 110 indicative oftongue movement in a patient.

Tongue movement may be defined or detected in various ways. For example,in one embodiment, tongue movement may be associated with a measurementof the absolute movement of the tongue with respect to external unit120. Alternatively, or in addition, tongue movement may be associatedwith a measurement of a relative displacement. For example, the distancebetween implant unit 110 and external unit 120 may vary over a certainrange, and a measurement of relative displacement of tongue movement mayinclude a representation of that range. Moreover, in a furtherembodiment, tongue movement may include a representation of the speedand/or direction at which the tongue is moving.

Processor 144 may accordingly be configured to determine whether thetongue movement is representative of a sleep disordered breathing basedon the signal received that is indicative of tongue movement. The sleepdisordered breathing may include, but is not limited to, an apneaprecursor, hypopnea, or a hypopnea precursor. Processor 144 may beconfigured to determine the occurrence of sleep disordered breathingprior to a total obstruction apnea event. That is, processor 144 may beconfigured to determine when a partial obstruction event occurs, respondto that partial obstruction event, and thereby prevent a totalobstruction apnea event from occurring. This determination may beaccomplished by the processor comparing the signal informationindicative of tongue movement to any suitable baseline from which asleep disordered breathing condition may be determined. For example, thebaseline may include data stored in a lookup table or other form ofaccessible database. The baseline may include data reflective of anormal tongue movement of the subject. Any suitable baseline may be usedto represent normal tongue movement and to enable a qualitative orquantitative determination of when a detected tongue movement variesfrom normal tongue movement and the degree to which the detected tonguemovement varies from normal tongue movement.

In some embodiments, the subject's normal tongue movement may bemonitored, and a baseline tongue movement profile may be determined andstored for use in detection of sleep disordered breathing events. Thisbaseline tongue movement profile may be determined, for example, uponactivation of external unit 120, upon placement of external unit 120 onthe skin of a patient relative to implant unit 110, etc. In someembodiments, activation of external unit 120 may include a calibrationperiod, during which processor 144 may be configured to monitor thepatient's normal tongue movement. Monitoring the normal tongue movementduring the calibration period may include, but is not limited to, ameasurement of the range of movement of the tongue during breathing, thespeed of movement of the tongue, and the absolute displacement ofimplant unit 110 from external unit 120.

Subsequent to the calibration period, processor 144 may be configured tomonitor movement of the subject's tongue and compare those movements tothe tongue movement profile obtained during calibration or to any othersuitable baseline tongue movement data. Processor 144 may be configuredto detect a sleep disordered breathing event when one or more detectedtongue movement characteristics (e.g., absolute displacement, directionof movement, velocity of movement, periodicity of vibratory oroscillatory movements, etc.) as compared to normal tongue movementparameters indicate the existence of a sleep disordered breathing event.

In response to a determination that the tongue movement isrepresentative of sleep disordered breathing, processor 144 may generatea modulation control signal (e.g., a stimulation control signal) tocorrect the sleep disordered breathing. The modulation control signalmay be applied, for example, to primary antenna 150 of external unit 120and may be configured to interact with secondary antenna 152 of implantunit 110 in order to generate a modulation signal within implant unit110. This modulation signal may cause activation of one or more nervesassociated with the tongue and may lead to contraction of theGenioglossus muscle associated with the tongue. Contraction of theGenioglossus muscle may move the tongue away from the subject's airwayto correct or avoid a sleep disordered breathing event.

Processor 144 may further be configured to adjust at least onecharacteristic of the modulation control signal based on a detectedseverity of the sleep disordered breathing. The severity of a sleepdisordered breathing condition may be determined, for example, based onanalysis of movement characteristics (e.g. absolute displacement,direction of movement, velocity of movement, periodicity of vibratory oroscillatory movements, etc.) associated with the tongue. The at leastone characteristic of the modulation control signal may include, but isnot limited to, voltage amplitude, current amplitude, pulse frequency,pulse duration, or any other suitable characteristic of the modulationcontrol signal.

In response to any of these determined physiologic data, processor 144may regulate delivery of power to implant unit 110 based on thedetermined physiologic data. For example, processor 144 may selectparameters such as, for example, the power level and/or duration for aparticular modulation control signal or series of modulation controlsignals for addressing a specific condition relating to the determinedphysiologic data. If the physiologic data indicates that the tongue isvibrating, for example, processor 144 may determine that a sleep apneaevent is likely to occur and may issue a response by delivering power toimplant unit 110 in an amount selected to address the particularsituation. If the tongue is in a position blocking the patient's airway(or partially blocking a patient's airway), but the physiologic dataindicates that the tongue is moving away from the airway, processor 144may opt to not deliver power and wait to determine if the tongue clearson its own. Alternatively, processor 144 may deliver a small amount ofpower to implant unit 110 (e.g., especially where a determined rate ofmovement indicates that the tongue is moving slowly away from thepatient's airway) to encourage the tongue to continue moving away fromthe patient's airway or to speed its progression away from the airway.Additionally or alternatively, processor 144 may deliver power toimplant unit 110 to initiate a tongue movement, monitor the movement ofthe tongue, and deliver additional power, for example, a reduced amountof power, if necessary to encourage the tongue to continue moving awayfrom the patient's airway. The scenarios described are exemplary only.Processor 144 may be configured with software and/or logic enabling itto address a variety of different physiologic scenarios withparticularity. In each case, processor 144 may be configured to use thephysiologic data to determine an amount of power to be delivered toimplant unit 110 in order to modulate nerves associated with the tonguewith the appropriate amount of energy.

In some embodiments, processor 144 may select the parameters of aparticular modulation control signal or series of modulation controlsignals based on the severity of a physiological condition. Severity ofa detected physiological condition may be defined as a deviation fromnormal range of the condition, and may be determined by a deviation in,for example, a position of certain tissue or body parts in a subject, arate of change or direction of change in a position of certain tissue orbody parts in a subject, blood oxygen level, blood glucose level, pulserate, and breathing rate or any other parameter of normal bodilyfunction.

Processor 144 may be configured to select the parameters of a particularmodulation control signal or series of modulation control signals basedon a function (either continuous or discontinuous) of the severity ofthe detected physiological condition. In a continuous function, themeasured severity may be mapped directly to variations in the powerlevel and/or duration of the modulation control signal based on atransfer function. The transfer function may be universal,predetermined, or may be calibrated for each individual subject. In adiscontinuous function, a look-up table may be used to determine anappropriate power level and/or duration of the modulation control signalfor severities within certain ranges.

In each case, processor 144 may be configured to use the severity of thephysiologic condition to determine an amount of power to be delivered toimplant unit 110 in order to modulate nerves associated with the tonguewith the appropriate amount of energy. Because the modulation controlsignal may be received in pulses by secondary antenna 152, the lengthand frequency of the pulses of the secondary signal generated onsecondary antenna 152 may also be varied. Variations in the secondarysignal may cause variations in the power level and/or duration of themodulation signal applied to electrodes 158 a, 158 b.

A method for regulating delivery of power to implant unit 110 mayinclude detecting a severity of a physiologic condition and determining,based on the severity of the physiologic condition, a power level and/orduration of the modulation signal or series of modulation signals. Forexample, tongue movement may be indicative of a sleep disorderedbreathing event, and the amount of tongue movement may be indicative ofa severity of the sleep disordered breathing event.

In some embodiments, a predetermined movement of implant unit 110 withthe tongue muscle 130 may trigger delivery of a modulation signal. Thepredetermined movement, as used here, refers to a distance threshold, avibratory amplitude/frequency threshold, or any other suitable thresholdparameter.

The power and/or duration of the modulation signal triggered by themovement of implant unit 110 may be dependent on the amount of movementof a subjects tongue. In some embodiment, tongue movement may beindicative of sleep disordered breathing, and the amount of tonguemovement may be indicative of a severity of a sleep disordered breathingevent. The amount of tongue movement may be determined based on theabsolute movement of tongue muscle 130 relative to external unit 120.Alternatively, the amount of tongue movement may be determined by therelative displacement of implant unit 110 and external unit 120. In someembodiments, the amount of tongue movement may also refer to the speedat which the tongue is moving, direction of tongue movement, andvibration of the tongue.

As previously discussed, the degree of coupling between primary antenna150 associated with external unit 120 and secondary antenna 152associated with implant unit 110, may be monitored in order to determinean amount of tongue movement. Processor 144 may be configured to monitorthe degree of coupling and regulate delivery of power from the externalunit 120 to the implant unit 110 based on the determined degree ofcoupling and/or determined amount of tongue movement. In someembodiment, processor 144 may be configured such that a predeterminedmovement of the at least one implantable circuit with the tonguetriggers delivery of a modulation control signal. Regulation of powerdelivery in this manner, in turn, may regulate the power level and/orduration of the modulation signal applied to electrodes 158 a, 158 b.

As previously discussed, the degree of coupling determination may enablethe processor to further determine a location of the implant unit. Themotion of the implant unit may correspond to motion of the body partwhere the implant unit may be attached. This may be consideredphysiologic data received by the processor. The processor may,accordingly, be configured to regulate delivery of power from the powersource to the implant unit based on the physiologic data. In alternativeembodiments, the degree of coupling determination may enable theprocessor to determine information pertaining to a condition of theimplant unit. Such a condition may include location as well asinformation pertaining to an internal state of the implant unit. Theprocessor may, according to the condition of the implant unit, beconfigured to regulate delivery of power from the power source to theimplant unit based on the condition data.

In some embodiments, implant unit 110 may include at least one processorlocated on the implant. A processor located on implant unit 110 mayperform all or some of the processes described with respect to the atleast one processor associated with an external unit. For example, aprocessor associated with implant unit 110 may be configured to receivea control signal prompting the implant controller to turn on and cause amodulation signal to be applied to the implant electrodes for modulatinga nerve. Such a processor may also be configured to monitor varioussensors associated with the implant unit and to transmit thisinformation back to and external unit. Power for the processor unit maybe supplied by an onboard power source or received via transmissionsfrom an external unit.

In other embodiments, implant unit 110 may be self-sufficient, includingits own power source and a processor configured to operate the implantunit 110 with no external interaction. For example, with a suitablepower source, the processor of implant unit 110 could be configured tomonitor conditions in the body of a subject (via one or more sensors orother means), determining when those conditions warrant modulation of anerve, and generate a signal to the electrodes to modulate a nerve. Thepower source could be regenerative based on movement or biologicalfunction; or the power sources could be periodically rechargeable froman external location, such as, for example, through induction.

In some embodiments, the at least one processor may be associated withmonitoring the degree of coupling can provide such physiologic data aswhether a patient's tongue is moving or vibrating. In one embodiment,for example, the degree of coupling may indicate physiologic datarelating to a distance between external unit 120 and implant unit 110,which processor 144 may use to determine a position of external unit 120or a relative position of a patient's tongue. The distance betweenexternal unit 120 and implant unit 110 may be determined along anysuitable and desired vector and/or combination of vectors.

The signals produced by the indicator 145 may permit a user to placeexternal unit 120 at an optimal location in relation to implant unit110. In one embodiment, indicator 145 may be configured to produce avariable signal (i.e., two or more signals) when external unit 120 iswithin a predetermined distance range of implant unit 110, such that thevariable signal may be configured to reach a maximum output whenexternal unit 120 is at an optimal distance from implant unit 110. Forexample, if the indicator signal is audible, it may be configured tochange pitch as external unit 120 is moved closer to implant unit 110,thereby reaching the highest, or alternatively, the lowest pitch, whenexternal unit 120 is at an optimal location. Further examples ofindicator signals may include, but are not limited to, beeps that changefrequencies, a light changing colors and/or getting brighter or dimmer,a tactile output (e.g. vibration) that increases or decreases instrength, or an electrical stimulating signal that increases ordecreases in strength. Of course, these signals are described asexamples only. There are nearly limitless forms of audible, visual,tactile, or other signals that can be configured to convey a degree ofcoupling between external unit 120 and internal uni 110.

In addition, or alternatively, the indicator 145 may be configured totransmit electrical signals directly to implant unit 110 in response toa determined degree of coupling. For example, once the determined degreeof coupling reaches a suitable level or exceeds a predeterminedthreshold, for example, the indicator 145 may cause a modulation controlsignal to be issued that causes modulation of a nerve in the subject'sbody. This modulation may be felt by the subject and may serve as anindication that external unit is properly positioned with respect toimplant unit 110.

The indicator 145 may further be configured to produce a signal whenexternal unit 120 is within a predetermined distance range of implantunit 110 or when a degree of coupling between external unit 120 andimplant unit 110 exceeds a predetermined threshold. The indicator 145may further be configured to provide a signal when external unit 120 isnot within a predetermined distance range of implant unit 110 or when adetermined degree of coupling between the two units falls below apredetermined threshold. For example, indicator 145 may be configured toproduce at least two signals: a first signal when external unit 120 iswithin a predetermined distance range of implant unit 110 or when adetermined coupling level exceeds a predetermined level and a second,different signal when external unit 120 is not within a predetermineddistance range of implant unit 110 or when the determined coupling leveldoes not exceed the predetermined level.

Implant unit 110 may be configured to deliver at power in at least afirst power mode and a second power mode. Power delivery in the firstpower mode and the second power mode may be configured in any suitablemanner in order to provide a desired response or performancecharacteristic. For example, in some embodiments, the level of powerdelivered in the first power mode and the second mode may be different.For example, the first power mode may be associated with a power levelthat is less than a power level associated with the second power mode.Any suitable power delivery scheme using at least the first power modeand second power mode may also be employed. For example, during atherapy period, power delivery in the first mode may be associated witha desired duty cycle such that power delivery in the first power modeoccurs over a total time that is greater than about 50% of the therapyperiod (e.g., while a subject is asleep). In some embodiments, however,the total time of power delivery in the first power mode may be greaterthan about 90% of the therapy period. The total time of power deliveryin the first power mode may also be greater than about 95% of thetherapy period.

Power may be supplied to implant unit 110 in any suitable form. In someembodiments, the at least one processor may be configured to cause powerto be delivered to implant unit 110 via an alternating current signal orvia a direct current signal. In embodiments where power is supplied viaan alternating current signal, implant unit 110 may include conversioncircuitry for converting the alternating current signal received, forexample, by secondary antenna 152 to a direct current signal to beapplied, for example to electrodes 158 a, b.

The power levels associated with each of the first and second powermodes may be selected to provide a desired response or performancecharacteristic of implant unit 110 and/or external unit 120. Forexample, in some embodiments, the power delivered to implant unit 110during the first power mode may be provided via a sub-stimulation orsub-modulation control signal applied to primary antenna 150. As notedabove, such sub-modulation control signals may include an amplitudeand/or duration that result in a sub-modulation signal at electrodes 158a, 158 b (e.g., a signal that produces little or no nerve modulation).While such sub-modulation control signals may not result in nervemodulation, such sub-modulation control signals may enablefeedback-based control of the nerve modulation system. That is, in someembodiments, processor 144 may be configured to cause application of asub-modulation control signal to primary antenna 150. This signal mayinduce a secondary signal on secondary antenna 152, which, in turn,induces a primary coupled signal component on primary antenna 150.

The sub-modulation control signal in the first power mode may be appliedin any suitable manner for achieving a desired operationalcharacteristic of either implant unit 110 or external unit 120 or fordetermining various parameters associated with implant unit 110 orexternal unit 120. For example, a sub-modulation control signal may beuseful in making impedance measurements, e.g., using standard RFcoupling techniques to detect the impedance between primary antenna 150and secondary antenna 152. In a first power mode, the energy sent mayinclude a low voltage AC signal (e.g., a sub-modulation control signal),to detect movement of the implant through coupling. As a sub-modulationcontrol signal, this low power AC signal may provide insufficient powerto activate the stimulation circuit. Diodes, e.g. diode 156 in FIG. 6,may be used to control whether the low voltage AC signal activates thestimulator. The low power AC signal, or sub-modulation control signal,may be constantly provided in order to continuously or periodicallydetect location and motion of implant unit 110 over a period of time.This signal, however, may be provided at a level below that needed toactivate diodes in the circuit of FIG. 6 (e.g., diode 156). With noactivation of the diodes, little or no current is passed to electrodes158 a, b.

The sub-modulation control signal may also be useful for monitoringasymmetric non-linearities generated through activation of diode 156.The non-linear diode 156 rectifies the signal appearing on secondaryantenna 152, which may result in the production of harmonics that may bedetected as one or more signal components induced on primary antenna150. These harmonics may be asymmetric in view of the half waverectification provided by diode 156. While the sub-modulation controlsignal may have an amplitude sufficient to cause forward biasing ofdiode 156, nerve modulation may be avoided by applying sub-modulationcontrol signal to primary antenna 150 using pulse durations that aresufficiently short to avoid nerve modulation.

The sub-modulation control signal may also be useful in monitoringsymmetric non linearities generated through activation of both diode 156and the Zener diodes 154 (FIG. 6). In such embodiments, the transmittedvoltage associated with the stab-modulation control signal may be highenough to activate both diode 156 and Zener diodes 154 such thatsymmetric, non-linear harmonics are generated. The pulse duration of thesub modulation control signal, however, may be short enough to avoidnerve modulation, and the zener diodes earlier in the circuit.

Monitoring the impedance, onset of non-linearities, or transitions fromasymmetric to symmetric non-linearities may provide informationregarding various aspects of implant unit 110. For example, suchinformation may enable determination of the position of implant unit 110with respect to external unit 120, relative direction of movement,velocity of movement, etc.

During the second power mode, the at least one processor may cause asecond alternating current signal (e.g., a modulation control signal) tobe applied to primary antenna 150 in order to supply power to implantunit 110. A signal induced on secondary antenna 152 in response to themodulation control signal may be supplied to the electrodes forgenerating an electromagnetic field. In some embodiments, the signal onsecondary antenna 152 may be converted to DC for application toelectrodes 158 a, b by either active or passive circuit components or byany other suitable method. The modulation control signal may beassociated with a power level higher than the sub-modulation controlsignal and/or a pulse length longer than the sub-modulation controlsignal. While the sub-modulation control signal may be useful formonitoring various characteristics associated with implant unit 110, themodulation control signal may be associated with a power level and/orpulse duration sufficient to cause modulation of at least one nerve inthe body of the subject.

In some embodiments, the pulse length of the sub-modulation controlsignal may be less than 50 microseconds or less than 500 nanoseconds.The pulse length of the modulation control signal may be greater than 50microseconds.

Either of the sub-modulation control signal or the modulation controlsignal may include any signal which may cause power to be supplied tothe implant. In some embodiments, these signals may includeelectromagnetic signals (e.g. microwave, infrared, radio-frequency (RF),etc.). These signals may include any suitable waveforms (e.g.sinusoidal, sawtooth wave, square wave, triangle wave) and may includeany suitable amplitude or duration which may achieve the desiredresults.

The first power mode may be implemented in any manner which may deliverless power than the power in the second power mode. In some embodiments,the first power mode may not provide enough, power to activate theimplant unit. For example, the first alternating current signal may besupplied at a lower voltage during the first power mode than thealternating current signal applied during the second power mode.

In the second power mode, the level of power delivered may be any levelgreater than the level of power in the first mode. In some embodiments,the power level in the second mode is sufficient to activate theimplant. The level of power transmitted in the second mode may besufficient to allow implant unit 110 to cause neural modulation throughthe electrodes associated with the implant circuit.

As used herein, references to an amount of power delivered may referboth to an instantaneous rate of energy transfer and a rate of energytransfer over a specific period of time. For example, at a constantcurrent, increasing the voltage of a signal will increase theinstantaneous rate of energy transfer of that signal, thereby increasingthe amount of power delivered. In an embodiment utilizing power deliveryin direct current pulses, an amount of power delivered may be increasedeven if voltage and current are held constant. Consider for example,power delivered in a series of direct current pulses over a specifiedtime period. Over the specified time period, direct current pulseshaving a greater length will deliver a greater amount of power than aseries of direct current pulses having a shorter length, even if theinstantaneous rate of energy transfer during each pulse is the same.That is, the amount of power delivered may be measured as a function ofenergy transferred over any appropriate length of time.

Physiologically, different methods of altering an amount of powerdelivered may be used in order to create a signal adapted to modulate(or not modulate) a nerve. For example, delivering less power tomodulation electrodes 158 a, 158 b via a signal with lower current mayresult in the generation of an electric field too weak to exceed themembrane potential threshold of neural ion channels, thus resulting inno modulation. Increasing the power via an increased current may serveto induce an electric field sufficient to cause modulation. Powerdelivery with an increased current, therefore, may be an example ofdelivering an amount of current sufficient to modulate a nerve. Inanother example, delivering less power to modulation electrodes 158 a,158 b by delivering shorter pulses without reducing the current mayresult in the generation of a short lived electric field. Such a shortlived electric field may not permit the ion channels in the field enoughtime to activate and pump sufficient ions across the plasma membrane inorder to propagate an action potential to neighboring ion channels. Thatis, the energy is transferred to the ion channel while the electricfield is being generated may be insufficient to modulate the nerve.Increasing the power delivery in such an embodiment by increasing thepulse lengths (such that the pulses facilitate an electric field ofsufficient duration to induce the propagation of an action potential)may constitute one example of power delivery in pulse lengths sufficientto cause neural modulation.

In some embodiments, the at least one processor may be in electricalcommunication with primary antenna 150 and configured to be locatedexternal to a subject. The at least one processor may also be configuredto receive a condition signal from an implantable device. In someembodiments, the condition signal may be indicative of a precursor tosleep disordered breathing. In response to the received conditionsignal, the at least one processor may cause transmission of a primarysignal from the primary antenna to the implantable device. In someembodiments, the primary signal may be used to stimulate at least onenerve (for example, a hypoglossal nerve) in response to a detectedprecursor to sleep disordered breathing. The primary antenna and the atleast one processor may also be associated with an external unit, forexample external unit 120.

The condition signal received from the implantable device (which may beconfigured to be implanted, for example, in the body of a subject andproximate to the subject's tongue) may include any signal or signalcomponent indicative of at least one condition associated with thesubject. In some embodiments, for example, the condition may indicatewhether a portion of the subject's body (e.g., the tongue) has moved, adirection of movement, a rate of change of movement, temperature, bloodpressure, etc. The condition signal may include any form of signalsuitable for conveying information associated with at least some aspectof the subject. In some embodiments, the condition signal may include anelectromagnetic signal (e.g. microwave, infrared, radio-frequency (RF),etc.) having any desired waveform (e.g. sinusoidal, square wave,triangle wave, etc.). The condition signal may include any suitableamplitude or duration for transferring information about the subject. Insome embodiments, the control signal may include a signal componentarising on primary antenna 150 as a result of coupling with secondaryantenna 152 on implant unit 110. For example, in some embodiments, thecondition signal may include a primary coupled signal component onprimary antenna 150. This primary coupled signal component may beinduced on primary antenna 150 through coupling between primary antenna150 of external unit 120 and secondary antenna 152 on implant unit 110.In other embodiments, the control signal may include signals transmittedto primary antenna 150 via one or more active transmitters in implantunit 110.

In some embodiments, the condition signal may be indicative of movementof a subject's tongue. For example, movement of the tongue may causerelative motion between primary antenna 150 and secondary antenna 152,and this relative motion may result in variation of a degree of couplingbetween primary antenna 150 and secondary antenna 152. In someembodiments, the condition signal may be indicative of the degree ofcoupling between the primary antenna 150 and secondary antenna 152associated with the implantable device. By monitoring the degree ofcoupling between primary antenna 150 and secondary antenna 152, forexample, by monitoring signals or signal components present on primaryantenna 150, relative movement between primary antenna 150 and secondaryantenna 152 (which may indicate relative movement between implantabledevice 110 and external unit 120, with which primary antenna 150 and theat least one processor are associated), and, therefore, movement of thesubject's tongue, may be detected. In some embodiments, the conditionsignal may be indicative of the subject's tongue over a predetermineddistance. Generally, however, the condition signal may indicate anycondition at least partially upon which a primary signal may be sent.

As noted, the at least one processor may cause a response based on thecondition signal. For example, in some embodiments, the at least oneprocessor may be configured to cause the generation of a primary signalintended to control at least one aspect of implant unit 110. The primarysignal may include a modulation control signal applied to primaryantenna 150 such that a resulting secondary signal on secondary antenna152 will provide a modulation signal at implant electrodes 158 a and 158b.

In some embodiments, the processor may be configured to detect a sleepdisordered breathing event based on the condition signal and send aprimary signal in response to the detected sleep disordered breathingevent. In some embodiments, the sleep disordered breathing event may bea precursor of sleep apnea or of sleep apnea-related airway blockage,and the primary signal may be predetermined to activate neuromusculartissue within the tongue. Such activation may cause movement of thesubject's tongue, for example, in a direction away from the posteriorpharyngeal wall. In some embodiments, transmission of the primary signalfrom primary antenna 150 to the implantable device 110 may occur priorto the sleep apnea airway blockage.

The primary signal may include any suitable characteristics for causinga desired response in implant unit 110. For example, the primary signalmay have any suitable amplitude, duration, pulse width, duty cycle, orwaveform (e.g. a sinusoidal signal, square wave, triangle wave, etc.)for causing a desired effect on implant unit 110 (e.g., modulation ofnerve tissue, for example a hypoglossal nerve, in the vicinity ofimplant unit 110, etc.).

In some embodiments, the desired effect may be achieved by supplying anelectrical signal to at least one pair of electrodes, for exampleelectrodes 158 a and 158 b, in the implantable device. The electrodesmay be configured to generate an electromagnetic field to stimulate theat least one nerve. In some embodiments, one electrode of each pair mayfunction as an anode (i.e. a positive electrode), and the otherelectrode of the pair may function as a cathode (i.e. a negativeelectrode). Implant unit 110 may be configured in a manner that promotesachievement of the desired effect. For example, in at least someembodiments, implant unit 110 may be configured such that when implantunit 110 is implanted into a subject, the electrodes of implant 110 willbe oriented such that an electromagnetic field generated from theelectrodes extends in an elongated direction of the at least one nerveto be stimulated. In some embodiments, the field is created, forexample, by forming a direct current (DC) pulse and providing it to oneor more pairs of electrodes.

Electromagnetic fields from the electrodes on implant unit 110 may begenerated in any suitable manner. In some embodiments, the at least oneprocessor may cause generation of a primary signal on primary antenna150, which, in turn, may cause a responsive signal to appear onsecondary antenna 152 through coupling. As discussed above, circuitry inimplant unit 110 may respond to the presence of a signal on thesecondary antenna and cause a signal to be applied to electrodes 158 aand 158 b. This applied signal at the electrodes may creates theelectromagnetic field for stimulating neuromuscular tissue in the bodyof a subject.

In some embodiments, the at least one processor may be associated withthe housing of external unit 120 and may be configured to communicatewith a circuit implanted in the subject. The at least one processor mayalso be configured to receive a physiological signal from the subjectvia the implanted circuit. In response to the received physiologicalsignal, the at least one processor may send a control signal, such as aclosed loop control signal, to the implanted circuit. In someembodiments, the control signal may be predetermined to activateneuromuscular tissue within the tongue. Activating neuromuscular tissuemay include, for example, causing muscular contractions and initiating anerve action potential.

The physiological signal received from the implant unit may include anysignal or signal component indicative of at least one physiologicalcharacteristic associated with the subject. In some embodiments, forexample, the physiological characteristic may indicate whether a portionof the subject's body (e.g., the tongue) has moved, a direction ofmovement, a rate of change of movement, temperature, blood pressure,etc. The physiological signal may include any form of signal suitablefor conveying information associated with at least some aspect of thesubject. In some embodiments, the physiological signal may include anelectromagnetic signal (e.g. microwave, infrared, radio-frequency (RF),etc.) having any desired waveform (e.g. sinusoidal, square wave,triangle wave, etc.). In some embodiments, the physiological signal mayinclude any suitable amplitude or duration for transferring informationabout the subject.

In some embodiments, the physiological signal may include a primarycoupled signal component on primary antenna 150. This primary coupledsignal component may be induced on primary antenna 150 through couplingbetween primary antenna 150 of external unit 120 and secondary antenna152 on implant unit 110.

In some embodiments, the physiological signal may include at least oneaspect indicative of a movement of the subject's tongue. For example,movement of the tongue may cause relative motion between primary antenna150 and secondary antenna 152, and this relative motion may result invariation of a degree of coupling between primary antenna 150 andsecondary antenna 152. By monitoring the degree of coupling betweenprimary antenna 150 and secondary antenna 152, for example, bymonitoring signals or signal components present on primary antenna 150,relative motion between primary antenna 150 and secondary antenna 152and, therefore, movement of the subject's tongue, may be detected.

As noted, in response to a received physiological signal, the at leastone processor may cause a response based on the physiological signal.For example, in some embodiments, the at least one processor may beconfigured to cause the generation of a control signal (e.g. a closedloop control signal) intended to control at least one aspect of implantunit 110. The control signal may include a modulation control signalapplied to primary antenna 150 such that a resulting secondary signal onsecondary antenna 152 will provide a modulation signal at implantelectrodes 158 a and 158 b.

In some embodiments, the processor may be configured to detect a sleepdisordered breathing event based on the physiological signal and sendthe closed loop control signal in response to the detected sleepdisordered breathing event. In some embodiments, the sleep disorderedbreathing event may be a precursor of sleep apnea, and the controlsignal may be predetermined to activate neuromuscular tissue within thetongue and may cause movement of the subject's tongue, for example, in adirection away from the posterior pharyngeal wall. The at least oneprocessor may be further configured to determine a severity of the sleepdisordered breathing event based on the physiological signal and vary apower level or duration of the control signal based on the determinedseverity of the sleep disordered breathing event. The severity of theevent may be determined, for example, based on a determination of therelative movement between primary antenna 150 and secondary antenna 152(e.g., an amplitude of movement, a rate of movement, a direction ofmovement, etc.). In some embodiments, a control signal may be sent ifthe relative movement exceeds a certain threshold.

A control signal may include any signal having suitable characteristicsfor causing a desired response in implant unit 110. For example, acontrol signal may have any suitable amplitude, duration, pulse width,duty cycle, or waveform (e.g. a sinusoidal signal, square wave, trianglewave, etc.) for causing a desired effect on implant unit 110 (e.g.,modulation of nerve tissue in the vicinity of implant unit 110, etc.). Acontrol signal may be generated and sent (e.g., to implant unit 110)within any desired response time relative to receipt of a physiologicalsignal. In some embodiments, the response time may be set at 1 second,500 milliseconds, 200 milliseconds, 100 milliseconds, 50 milliseconds,20 milliseconds, 5 milliseconds, 1 millisecond, or any other timegreater than 0 seconds and less than about 2 seconds. The control signalmay be closed loop. As used herein, the term closed loop control signalmay refer to any signal at least partially responsive to another signal,such as a control signal sent in response to a physiological signal. Orit may include any feedback response.

Based on the physiological signal, the processor may determine aquantity of energy to be sent via the closed loop control signal toimplant unit 110. The amount of energy to be sent may be determinedand/or varied based on any relevant factor including, for example, thetime of day, a relevant biological factor of the subject (bloodpressure, pulse, level of brain activity, etc.), the severity of thedetected event, other characteristics associated with the detectedevent, or on any combination of factors. As noted, in embodiments wherethe physiological signal indicates a sleep disordered breathing event,the processor may be configured to determine a severity of the sleepdisordered breathing event based on the physiological signal. In suchembodiments, the processor may also determine an amount of energy to beprovided to implant unit 110 as a response to the detected sleepdisordered breathing event and in view of the determined severity of theevent. The determined amount of energy may be transferred to implantunit 110 over any suitable time duration and at any suitable powerlevel. In some embodiments, the power level and/or the duration of thecontrol signal may be varied, and such variation may be dependent on thedetermined severity of the sleep disordered breathing event.

The power level and/or duration of the control signal may also bedetermined based on other factors. For example, the processor may vary apower level or duration associated with the control signal based on theefficiency of energy transfer between external unit 120 and implant unit110. The processor may have access to such information throughpre-programming, lookup tables, information stored in memory, etc.Additionally or alternatively, the processor may be configured todetermine the efficiency of energy transfer, e.g., by monitoring theprimary coupled signal component present on primary antenna 150, or byany other suitable method.

The processor may also vary the power level or duration of the controlsignal based on the efficacy of implant unit 110 (e.g., the implantunit's ability to produce a desired effect in response to the controlsignal). For example, the processor may determine that a certain implantunit 110 requires a certain amount of energy, a control signal of atleast a certain power level and/or signal duration, etc., in order toproduce a desired response (e.g., a modulation signal having anamplitude/magnitude of at least a desired level, etc.). Such adetermination can be based on feedback received from implant unit 110 ormay be determined based on lookup tables, information stored in memory,etc. In some embodiments, the power level or duration of the controlsignal may be determined based on a known or feedback-determinedefficacy threshold (e.g., an upper threshold at or above which a desiredresponse may be achieved) associated with implant unit 110.

In some embodiments, implant unit 110 may be structurally configured tofacilitate implantation in a location so as to increase the efficacy ofmodulation provided. For example, FIGS. 12 and 13 illustrate the anatomyof neck and tongue, and depict implantation locations suitable forneuromodulation treatment of OSA. FIG. 14 illustrates an exemplaryimplant unit 110 structurally configured for the treatment of head pain.FIGS. 15 and 16 illustrate exemplary implant units 110 structurallyconfigured for the treatment of hypertension.

FIG. 12 depicts an implantation location in the vicinity of agenioglossus muscle 1060 that may be accessed through derma on anunderside of a subject's chin. FIG. 12 depicts hypoglossal nerve (i.e.cranial nerve XII). The hypoglossal nerve 1051 through its lateralbranch 1053 and medial branch 1052, innervates the muscles of the tongueand other glossal muscles, including the genioglossus 1060, thehyoglossus 1062, mylohyoid (not shown) and the geniohyoid 1061 muscles.The mylohyoid muscle, not pictured in FIG. 12, forms the floor of theoral cavity, and wraps around the sides of the genioglossus muscle 1060and the geniohyoid 1061 muscles. The horizontal compartment of thegenioglossus 1060 is mainly innervated by the medial terminal fibers1054 of the medial branch 1052, which diverges from the lateral branch1053 at terminal bifurcation 1055. The distal portion of medial branch1052 then variegates into the medial terminal fibers 1054. Contractionof the horizontal compartment of the genioglossus muscle 1060 may serveto open or maintain a subject's airway. Contraction of other glossalmuscles may assist in other functions, such as swallowing, articulation,and opening or closing the airway. Because the hypoglossal nerve 1051innervates several glossal muscles, it may be advantageous, for OSAtreatment, to confine modulation of the hypoglossal nerve 1051 to themedial branch 1052 or even the medial terminal fibers 1054 of thehypoglossal nerve 1051. In this way, the genioglossus muscle, mostresponsible for tongue movement and airway maintenance, may beselectively targeted for contraction inducing neuromodulation.Alternatively, the horizontal compartment of the genioglossus muscle maybe selectively targeted. The medial terminal fibers 1054 may, however,be difficult to affect with neuromodulation, as they are located withinthe fibers of the genioglossus muscle 1061. Embodiments of the presentinvention facilitate modulation the medial terminal fibers 1054, asdiscussed further below.

In some embodiments, implant unit 110, including at least one pair ofmodulation electrodes, e.g. electrodes 158 a, 158 b, and at least onecircuit may be configured for implantation through derma (i.e. skin) onan underside of a subject's chin. When implanted through derma on anunderside of a subject's chin, for example, into a sub-mandibularregion, an implant unit 110 may be located proximate to medial terminalfibers 1054 of the medial branch 1052 of a subject's hypoglossal nerve1051. An exemplary implant location 1070 is depicted in FIG. 12.

In some embodiments, implant unit 110 may be configured such that theelectrodes 158 a, 158 b cause modulation of at least a portion of thesubject's hypoglossal nerve through application of an electric field toa section of the hypoglossal nerve 1051 distal of a terminal bifurcation1055 to lateral and medial branches 1053, 1052 of the hypoglossal nerve1051. In additional or alternative embodiments, implant unit 110 may belocated such that an electric field extending from the modulationelectrodes 158 a, 158 b can modulate one or more of the medial terminalfibers 1054 of the medial branch 1052 of the hypoglossal nerve 1051.Thus, the medial branch 1053 or the medial terminal fibers 1054 may bemodulated so as to cause a contraction of the genioglossus muscle 1060,which may be sufficient to either open or maintain a patient's airway.When implant unit 110 is located proximate to the medial terminal fibers1054, the electric field may be configured so as to cause substantiallyno modulation of the lateral branch of the subject's hypoglossal nerve1051. This may have the advantage of providing selective modulationtargeting of the genioglossus muscle 1060.

As noted above, it may be difficult to modulate the medial terminalfibers 1054 of the hypoglossal nerve 1051 because of their locationwithin the genioglossus muscle 1060. Implant unit 110 may be configuredfor location on a surface of the genioglossus muscle 1060. Electrodes158 a, 158 b, of implant unit 110 may be configured to generate aparallel electric field 1090, sufficient to cause modulation of themedial terminal branches 1054 even when electrodes 158 a, 158 b are notin contact with the fibers of the nerve. That is, the anodes and thecathodes of the implant may be configured such that, when energized viaa circuit associated with the implant 110 and electrodes 158 a, 158 b,the electric field 1090 extending between electrodes 158 a, 158 b may bein the form of a series of substantially parallel arcs extending throughand into the muscle tissue on which the implant is located. A pair ofparallel line electrodes or two series of circular electrodes may besuitable configurations for producing the appropriate parallel electricfield lines. Thus, when suitably implanted, the electrodes of implantunit 110 may modulate a nerve in a contactless fashion, through thegeneration of parallel electric field lines.

Furthermore, the efficacy of modulation may be increased by an electrodeconfiguration suitable for generating parallel electric field, linesthat run partially or substantially parallel to nerve fibers to bemodulated. In some embodiments, the current induced by parallel electricfield lines may have a greater modulation effect on a nerve fiber if theelectric field lines 1090 and the nerve fibers to be modulated arepartially or substantially parallel. The inset illustration of FIG. 12depicts electrodes 158 a and 158 b generating electric field lines 1090(shown as dashed lines) substantially parallel to medial terminal fibers1054.

In order to facilitate the modulation of the medial terminal fibers1054, implant unit 110 may be designed or configured to ensure theappropriate location of electrodes when implanted. An exemplaryimplantation is depicted in FIG. 13.

For example, a flexible carrier 161 of the implant may be configuredsuch that at least a portion of a flexible carrier 161 of the implant islocated at a position between the genioglossus muscle 1060 and thegeniohyoid muscle 1061. Flexible carrier 161 may be further configuredto permit at least one pair of electrodes arranged on flexible carrier161 to lie between the genioglossus muscle 1060 and the mylohyoidmuscle. Either or both of the extensions 162 a and 162 b of elongate arm161 may be configured adapt to a contour of the genioglossus muscle.Either or both of the extensions 162 a and 162 b of elongate arm 161 maybe configured adapt to a contour of the genioglossus muscle. Either orboth of the extensions 162 a and 162 b of elongate arm 161 may beconfigured to extend away from the underside of the subject's chin alonga contour of the genioglossus muscle 1060. Either or both of extensionarms 162 a, 162 b may be configured to wrap around the genioglossusmuscle when an antenna 152 is located between the genioglossus 1060 andgeniohyoid muscle 1061. In such a configuration, antenna 152 may belocated in a plane substantially parallel with a plane defined by theunderside of a subject's chin, as shown in FIG. 13.

Flexible carrier 161 may be configured such that the at least one pairof spaced-apart electrodes can be located in a space between thesubject's genioglossus muscle and an adjacent muscle. Flexible carrier161 may be configured such that at least one pair of modulationelectrodes 158 a, 158 b is configured for implantation adjacent to ahorizontal compartment 1065 of the genioglossus muscle 1060. Thehorizontal compartment 1065 of the genioglossus 1060 is depicted in FIG.13 and is the portion of the muscle in which the muscle fibers run in asubstantially horizontal, rather than vertical, oblique, or transversedirection. At this location, the hypoglossal nerve fibers run betweenand in parallel to the genioglossus muscle fibers. In such a location,implant unit 110 may be configured such that the modulation electrodesgenerate an electric field substantially parallel to the direction ofthe muscle fibers, and thus, the medial terminal fibers 1054 of thehypoglossal nerve in the horizontal compartment.

FIG. 14 depicts an exemplary implant location for the treatment of headpain. As illustrated in FIG. 14, implant unit 510 includes an elongatedcarrier 561, secondary antenna 552, and modulation electrodes 558 a, 558b. Implant unit 510 may also include any elements, such as circuitry,electrical components, materials, and any other features describedpreviously with respect to implant unit 110. Implant 510 may be sizedand configured such that it may be implanted with an end havingsecondary antenna 552 located beneath the skin in a substantiallyhairless region 507 of a subject. Elongated flexible carrier 561 mayextend from this location, across a hairline 502 of the subject, to alocation beneath the skin in a substantially haired region 506 of thesubject in a vicinity of an occipital or other nerve that may bemodulated to control or reduce head pain, such as a greater occipitalnerve 501 or a lesser occipital nerve 503. As used herein, the term“substantially haired region” includes areas of a subject's head locatedon a side of the hairline where the scalp hair is located on a typicalsubject. Thus, a bald person may still have a “substantially hairedregion” on the side of the hairline on which hair typically grows. Asused herein, the term “substantially hairless region” includes areas ofa subject's head located on a side of the hairline where the scalp hairis not located on a typical subject. A “substantially hairless region,”as used herein, is not required to be completely hairless, as almost allskin surfaces have some hair growth. As illustrated in FIG. 14, asubstantially haired region 506 is separated from a substantiallyhairless region 507 by a hairline 502.

As described above, implant 510 may extend across the hairline 502 to alocation in the vicinity of an occipital nerve. In FIG. 14, implant 510extends across the hairline 502 to a location in the vicinity of greateroccipital nerve 501. Furthermore, implant 510 may be configured forimplantation such that electrodes 558 a and 558 b are spaced from eachother along a longitudinal direction of an occipital nerve, such as thegreater occipital nerve 501 shown in FIG. 14. Such a configurationpermits electrodes 558 a and 558 b to facilitate an electrical fieldthat extends in the longitudinal direction of the occipital nerve. Inturn, the facilitated electrical field may be utilized to modulategreater occipital nerve 501, for example to block pain signals, aspreviously described.

The size and configuration of implant 510 illustrated in FIG. 14 maypermit secondary antenna 552 to be located beneath the skin in alocation where an external unit 520 (not illustrated), may be easilyaffixed to the skin, due to the lack of hair. External unit 520 mayinclude any elements, such as circuitry, processors, batteries,antennas, electrical components, materials, and any other featuresdescribed previously with respect to external unit 120. External unit520 may be configured to communicate with implant 510 via secondaryantenna 552 to deliver power and control signals, as described abovewith respect to external unit 120. Elongated carrier 561 may beflexible, and may permit modulation electrodes 558 a and 558 b to belocated beneath the skin in a location suitable for modulating anoccipital or other nerve for controlling head pain.

FIG. 15 depicts an exemplary implant location for the treatment ofhypertension. As illustrated in FIG. 15, implant unit 610 may beconfigured for location or implantation inside a blood vessel. Such aconfiguration may include, for example, a flexible tubular carrier.Implant unit 610 may also include any elements, such as circuitry,electrical components, materials, and any other features describedpreviously with respect to implant unit 110. Implant unit 610 mayinclude modulation electrodes 658 a, 658 b configured to facilitate anelectric field including field lines extending in the longitudinaldirection of the blood vessel. For example, as illustrated in FIG. 13,implant unit 610 may be implanted in a carotid artery 611. Implant unit610 may be located within carotid artery 611 in a location in thevicinity of carotid baroreceptors 615, at a location near the branchingof the internal carotid artery 613 and the external carotid artery 612.As described previously, carotid baroreceptors 615 aid in the regulationof the blood pressure of a subject. Thus, implant unit 610, locatedwithin carotid artery 611 in the vicinity of carotid baroreceptors 615may facilitate an electric field configured to modulate carotidbaroreceptors 615, and, thus, affect the blood pressure of a subject.Affecting the blood pressure of a subject may include reducing,increasing, controlling, regulating, and influencing the blood pressureof a subject. The illustrated location is exemplary only, and implantunit 610 may be configured in alternate ways. For example, implant unit610 may be configured for implantation in jugular vein 614 of thesubject, in a location from which modulation of carotid baroreceptors615 may be accomplished. Furthermore, implant unit 610 may be configuredfor implantation in a blood vessel, such as carotid artery 611 orjugular vein 614, in a location suitable for modulation ofglossopharyngeal nerve 615. As described above, glossopharyngeal nerve615 innervates carotid baroreceptors 615. Thus, glossopharyngeal nerve615 may be directly modulated to affect blood pressure of a subject.Glossopharyngeal nerve 615 may also be modulated by an implant unit 610located in a sub-cutaneously, in a non-intravascular location.

FIG. 16 depicts another exemplary implant location for the treatment ofhypertension. As illustrated in FIG. 16, implant unit 710 may beconfigured for location or implantation inside a blood vessel. Such aconfiguration may include, for example, a flexible tubular carrier.Implant unit 710 may also include any elements, such as circuitry,electrical components, materials, and any other features describedpreviously with respect to implant unit 110. Implant unit 710 mayinclude modulation electrodes 758 a, 758 b configured to facilitate anelectric field including field lines extending in the longitudinaldirection of the blood vessel. For example, as illustrated in FIG. 15,implant unit 710 may be implanted in a renal artery 711. Implant unit710 may be located within renal artery 711 in a location in the vicinityof renal nerves 715 surrounding renal artery 711 prior to its entry intokidney 712. As described previously, renal nerves 715 aids in theregulation of the blood pressure in humans. Thus, implant unit 710,located within renal artery 711 in the vicinity of renal nerves 715 mayfacilitate an electric field configured to modulate renal nerves 715,and, thus, affect the blood pressure of a subject. The illustratedlocation is exemplary only, and implant unit 710 may be configured inalternate ways suitable for the modulation of renal nerves 715.

Additional embodiments of the present disclosure may include thefollowing. A method of activating neuromuscular tissue with an implantedcircuit, comprising: communicating with the implanted circuit, which isimplanted within a proximity of a tongue of a subject, wherein theimplanted circuit is in electrical communication with at least oneelectrode; receiving a physiological signal from the subject via theimplanted circuit; sending a control signal to the implanted circuit inresponse to the physiological signal; and activating neuromusculartissue within the tongue of the subject via the control signal. Thecontrol signal may be sent within a response time chosen from among thegroup comprising 1 second, 500 milliseconds, 200 milliseconds, 100milliseconds, 50 milliseconds, 20 milliseconds, 5 milliseconds, and 1millisecond. The physiological signal may be received by a unit locatedexternal to the body of the subject, and the control signal is sent fromthe unit. The physiological signal may include at least one aspectindicative of a movement of the tongue. The movement of the tongue maybe detected via a relative motion between an antenna located external tothe body of the subject and an antenna associated with the implantedcircuit. The method of claim may, further comprise determining, based onthe physiologic signal, a quantity of energy to be sent to the implantedcircuit via the control signal. The method may further comprisedetecting a sleep disordered breathing event based on the physiologicalsignal; and generating the control signal to be sent based on thedetected sleep disordered breathing event. Generating the control signalto be sent may include determining a power level for the control signalbased on a determined severity of the sleep disordered breathing event.Generating the control signal to be sent may include determining a timeduration for the control signal based on a determined severity of thesleep disordered breathing event. The sleep disordered breathing eventmay be a precursor of sleep apnea. Activating neuromuscular tissuewithin the tongue may cause the subject's tongue to move in a directionaway from a posterior pharyngeal wall of the subject. The physiologicalsignal may be indicative of an efficiency of energy transfer between thehousing and the circuit, and generating the control signal to be sentmay include determining a power level based on the efficiency of energytransfer and an upper threshold associated with the implant circuit. Thephysiological signal may be indicative of an efficiency of energytransfer between the housing and the circuit, and generating the controlsignal to be sent may include determining a power level based on theefficiency of energy transfer and an efficacy threshold associated withthe implant circuit.

Additional embodiments of the present disclosure may include thefollowing. A method of modulating a hypoglossal nerve may comprisereceiving an alternating current (AC) signal at an implant unit,generating a voltage signal in response to the AC signal, applying thevoltage signal to at least one pair of modulation electrodes, the atleast one pair of modulation electrodes being configured to be implantedinto the body of a subject in the vicinity of the hypoglossal nerve, andgenerating an electrical field in response to the voltage signal appliedto the at least one pair of modulation electrodes to modulate thehypoglossal nerve from a position where the at least one pair ofmodulation electrodes do not contact the hypoglossal nerve. The ACsignal may be received via an antenna associated with the implant unit.The electric field generated by the at least one pair of modulationelectrodes may be configured to penetrate tissue in order to inducemodulation of the hypoglossal nerve. The tissue may include agenioglossus muscle. The at least one pair of modulation electrodes maybe configured such that the generated electric field provides an energydensity sufficient to modulate the hypoglossal nerve without contactingthe hypoglossal nerve. The voltage signal applied to the at least onepair of modulation electrodes may have a voltage of between about 0.5volts and about 40 volts. Each of the electrodes of the at least onepair of modulation electrodes may includes surface area of about 0.01mm² to about 80 mm². The electrodes of the at least one pair ofmodulation electrodes may be separated from one another by a distance ofless than about 25 mm.

Alternative embodiments consistent with the present disclosure mayinclude the following. A method of locating an external unit withrespect to an implant unit may comprise detecting a distance between theexternal unit and the implanted unit located beneath the skin of asubject, and producing an indicator signal when the external unit iswithin a predetermined range of the implant unit, and varying theindicator signal as a function of a distance between the external unitand the implant unit. The indicator signal may include a visual output.The indicator signal may include a tactile output. The indicator signalmay include an electrical signal communicated to the implant unit. Theelectrical signal may cause the implant unit to modulate a nerve and toinduce at least one of a proprioceptive or kinesthesic reaction in thesubject. The indicator signal may include an audible output. The methodmay further comprise generating a primary signal on a primary antennaassociated with the external unit, the primary signal being configuredto cause a secondary signal on a secondary antenna associated with theimplant unit, determining a degree of coupling between the primaryantenna associated with the external unit and the secondary antennaassociated with the implant unit, determining the distance between theexternal unit and the implant unit based on the degree of coupling, andcausing the indicator to produce the indicator signal when the degree ofcoupling exceeds a predetermined threshold. Determining the degree ofcoupling between the primary antenna associated with the external unitand the secondary antenna associated with the implant unit may includeat least one of determining a degree of capacitive coupling, a degree ofradio frequency coupling, or a degree of inductive coupling between theprimary antenna and the secondary antenna. The external unit maycomprise at least one processor; the at least one processor beingconfigured to generate a primary signal on a primary antenna associatedwith the external unit, the primary signal being configured to cause asecondary signal on a secondary antenna associated with the implantunit, determine a degree of coupling between the primary antennaassociated with the external unit and the secondary antenna associatedwith the implant unit, and cause the indicator to produce the indicatorsignal when the degree of coupling does not exceed a predeterminedthreshold.

A glucose monitoring device for measuring a level of glucose in asubject, the glucose monitoring device may comprise a housing configuredfor location on a a subject to communicate with an implantable glucosesensor implanted in the subject, and an indicator associated with thehousing, wherein the indicator is configured to produce an indicatorsignal when the housing is within a predetermined range of the implantunit, and wherein the indicator is configured to vary the indicatorsignal according to a distance between the housing and the implant unit.The housing may comprise at least one processor; the at least oneprocessor being configured to: generate a primary signal on a primaryantenna associated with the housing, the primary signal being configuredto cause a secondary signal on a secondary antenna associated with theimplant unit, determine a degree of coupling between the primary antennaassociated with the housing and the secondary antenna associated withthe implant unit, and cause the indicator to produce the indicatorsignal when the degree of coupling exceeds a predetermined threshold,operate in a placement mode and a monitoring mode, cause the indicatorto produce the variable signal during operation in the placement mode,and transition from the placement mode to the monitoring mode when acorrect placement condition is satisfied. The correct placementcondition may include at least one of a predetermined coupling thresholdand a predetermined timing threshold. The glucose monitoring device mayfurther comprise a skin patch, wherein the skin patch comprises anadhesive and is configured for adherence to the skin of the subject,wherein the housing is removably connected to the skin patch, and the atleast one processor is configured to operate in a placement mode whenthe housing is connected to the skin patch.

Additional embodiments of the present disclosure may include a method ofmodulating a nerve via at least one pair of electrodes associated withan implanted circuit and implanted in the vicinity of the nerve. Themethod may include steps of delivering to the electrodes, via theimplanted circuit, an electrical signal having a current less than about1.6 milliamps and modulating the nerve via the generation of anelectrical field between the electrodes by the electrical signal havinga current less than about 1.6 milliamps. The method may further includedelivering a plurality of electrical signals to the electrodes, whereineach of the plurality of electrical signals has a current less thanabout 1.6 milliamps. The method may further include, further comprisingvarying at least one of a voltage, current, or duration of the pluralityof electrical signals. The method may further include receiving, via theimplantable circuit, energy from a source external to a subject. Themethod may further include delivering to the electrodes, via theelectrical signal having a current less than about 1.6 milliamps, asubstantial portion of the energy received from the source external tothe subject within about 1 second or less of receiving the energy. Themethod may further include providing an implantable antenna, inelectrical communication with the implantable circuit, for transmittingor receiving electrical signals. The method may further includegenerating and sending, via a transmitter included in the implantablecircuit, a signal indicative of a request that energy be supplied fromthe source external to the subject. The implantable circuit may beconfigured for location detection from a location external to thesubject. The circuit and the electrodes may be further configured forimplantation in a subject on the surface of non-nerve tissue interposedbetween the electrodes and the nerve. The tissue interposed between theelectrodes and the nerve may include at least one of muscle tissue,connective tissue, fat, blood vessel, and mucosal membrane.

*** Additional embodiments of the present disclosure may include amethod for regulating delivery of power to an implant unit. The methodmay include communicating with the implant unit, which is implanted in abody of a subject, determining a degree of coupling between a primaryantenna associated with a power source and a secondary antennaassociated with the implant unit, and regulating delivery of power fromthe power source to the implant unit based on the degree of coupling.The method may further include receiving physiologic data via theimplant unit, and regulating delivery of power from the power source tothe implant unit based on the physiologic data and the degree ofcoupling. The upper limit of the power delivered from the power sourceto the implant unit may be determined according to an upper thresholdassociated with the implant unit. The lower limit of the power deliveredfrom the power source to the implant unit may be determined according toan efficacy threshold of the power delivered. The power may be deliveredfrom the power source to the implant unit via radiofrequencytransmission of an alternating current signal. Regulating delivery ofpower from the power source to the implant unit may include adjusting atleast one of voltage, pulse rate, and current associated with thealternating current signal. The degree of coupling between the primaryantenna and the secondary antenna may include a measure of capacitivecoupling. The degree of coupling between the primary antenna and thesecondary antenna may include a measure of radiofrequency coupling. Thedegree of coupling between the primary antenna and the secondary antennamay include a measure of inductive coupling. The physiologic data may berepresentative of a motion of the implant unit.

Additional embodiments of the present disclosure may include a method ofdelivering electrical stimulation treatment pulses, including generatinga primary signal in a primary antenna using power supplied by a battery,wherein the primary antenna is associated with a housing configured toretain the battery, and transmitting the primary signal from the primaryantenna to an implantable device during a treatment session of at leastthree hours in duration, wherein the primary signal includes a pulsetrain, the pulse train including a plurality of stimulation pulses. Theat least one of the plurality of stimulation pulses may include analternating current signal. The alternating current signal may have afrequency between 6.5 and 13.6 megahertz. The at least one of theplurality of stimulation pulses may include a plurality of stimulationsub-pulses, each stimulation sub-pulse having a duration of between 50and 250 microseconds. The at least one of the plurality of stimulationpulses may include between 5 and 15 stimulation sub-pulses. The at leastone processor may be configured to cause transmission of the primarysignal for at least 90% of the treatment session. The battery may have acapacity of less than 240 mAh, less than 120 mAh, and less than 60 mAh.The pulse train may include more than at least one of 5000, 10,000, and100,000 stimulation pulses. The temporal spacing between a majority ofthe stimulation pulses may be less than 1.3 seconds. The stimulationpulses occur at a frequency chosen from among four, eight, and sixteentimes a breathing frequency. The majority of the stimulation pulses mayhave a pulse duration of at least 200 milliseconds. At least one of thehousing and the primary antenna may be flexible to an extent permittingit to generally conform to the contours of a subject's skin. Theimplantable device may include at least one pair of stimulationelectrodes, and may be configured to cause a muscular contractioninducing current at the at least one pair of stimulation electrodes whenthe primary signal is received by the implantable device. Thestimulation pulses may be temporally spaced so as not to permit acomplete relaxation of a muscle after muscular contraction.

Additional embodiments of the present disclosure may include thefollowing. A method of transmitting signals to an implantable device maycomprise determining one or more sub-modulation characteristics of asub-modulation control signal so as not to cause a neuromuscularmodulation inducing current across at least one pair of modulationelectrodes in electrical communication with an implantable device whenthe sub-modulation control signal is received by the implantable device,determining one or more modulation characteristics of a modulationcontrol signal so as to cause a neuromuscular modulation inducingcurrent across at least one pair of modulation electrodes in electricalcommunication with the implantable device when the modulation controlsignal is received by the implantable device, generating the modulationcontrol signal having the one or more modulation characteristics,generating the sub-modulation control signal having the one or moresub-modulation characteristics, transmitting, via the primary antenna,the modulation control signal to a secondary antenna associated with theimplantable device, and transmitting, via the primary antenna, thesub-modulation control signal to a secondary antenna associated with theimplantable device. The method may further comprise receiving via theprimary antenna a condition signal from the implantable device. Thecondition signal may be indicative of at least one of movement of theimplantable device, a location of the implantable device, a maximumpower limit of the implantable device, and a minimum efficacy thresholdof the device. The one or more modulation characteristics of themodulation control signal and the one or more sub-modulationcharacteristics of the sub-modulation control signal may include atleast one of a voltage, current, frequency, pulse rate, pulse width, andduration. Transmission of at least one of modulation signal and thesub-modulation signal may be triggered by the condition signalindicative of a predetermined amount of movement of the implantabledevice. Movement of the implantable device may be indicative of anamount of tongue movement associated with sleep disordered breathing andthe amount of tongue movement may be indicative of a severity of thesleep disordered breathing. The condition signal may be indicative of adegree of coupling between the primary antenna and a secondary antennaassociated with the implantable device, the degree of coupling relatingto at least one of a level of radiofrequency coupling, a level ofinductive coupling, and a measure of harr nonic resonance. Thesub-modulation characteristics of the sub-modulation control signal maybe determined so as to elicit the condition signal from the implantabledevice. The method may further comprise adjusting at least one of theone or more modulation characteristics of the modulation control signaland the one or more sub-modulation characteristics of the sub-modulationcontrol signal based on the condition signal.

Additional embodiments consistent with the present disclosure mayinclude the following. A device, including an implantable flexiblecarrier, an implantable suit, and, a pair of electrodes located on thecarrier and in electrical communication with the implantable circuit.The electrodes may be configured to cause, when supplied with anelectrical signal via the implantable circuit, a unidirectionalelectrical field. The pair of electrodes may be further configured tomodulate the at least one nerve when non-nerve tissue is interposedbetween the electrodes and the at least one nerve. The electrodes may beconfigured with a spacing distance such that the unidirectionalelectrical field is sufficient to modulate at least one nerve locatedgreater than 1 mm away from the electrodes. The flexible carrier mayinclude attachment points configured for securing the flexible carrierto a surface of the non-nerve tissue. The flexible carrier may comprisean insulative coating, and the electrodes may be exposed on one side ofthe flexible carrier. The device may further include at least one pairof additional electrodes. The device may further include an antenna inelectrical communication with the implantable circuit, wherein theantenna is adapted to receive a transmitted alternating current signaland a converter configured to convert the alternating current signalinto a direct current signal for delivery to the at least one pair ofimplantable electrodes. The implantable circuit may located on theflexible carrier, and the antenna may be located on the flexiblecarrier.

Additional embodiments of the present disclosure may include thefollowing. A sleep disordered breathing therapy implant unit maycomprise a flexible carrier, at least one pair of modulation electrodeson the flexible carrier, and at least one implantable circuit inelectrical communication with the at least one pair of modulationelectrodes, wherein the at least one pair of modulation electrodes andthe at least one circuit are configured for implantation through dermaon an underside of a subjects chin, and wherein the implantable circuitand the electrodes are configured to cooperate in order to generate anelectric field adapted to cause modulation of at least a portion of thesubjects hypoglossal nerve through application of an electric field to asection of the hypoglossal nerve distal of a terminal bifurcation tolateral and medial branches of the hypoglossal nerve. The at least onepair of modulation electrodes may be configured to cause modulation ofat least a portion of the medial branch of the hypoglossal nerve. The atleast one pair of modulation electrodes may be configured to causemodulation of one or more terminal branches of the medial branch of thehypoglossal nerve.

Additional embodiments of the present disclosure may include a methodfor delivering power to an implanted circuit including communicatingwith the implanted circuit, which is implanted in a body of a subject,and transmitting power to the implanted circuit in a first power modeand in a second power mode, wherein a first level of power delivered inthe first power mode is less than a second level of power delivered inthe second power mode, and wherein during a therapy period, powerdelivery in the first power mode occurs over a total time that isgreater than about 50% of the therapy period. The implanted circuit maybe associated with electrodes, and during the first power mode,transmitting power may include transmitting a first alternating currentsignal to supply power to the implant circuit while the implant circuitis substantially restricted from supplying direct current to theelectrodes, and during the second power mode, transmitting power mayinclude transmitting a second alternating current signal to supply powerto the implant circuit for conversion to direct current to be suppliedto the electrodes. The implant circuit may be substantially restrictedfrom supplying direct current to the electrodes by a diode. During thefirst power mode, the first alternating current signal may betransmitted at a lower voltage than the second alternating currentsignal transmitted during the second power mode. The implant circuit maybe associated with electrodes, and transmitting power may includetransmitting an alternating current signal to the implant circuit forconversion to direct current to be supplied to the electrodes, andduring the first power mode, a first power mode pulse length of thealternating current signal may be shorter than a pulse length requiredto cause neural modulation through the electrodes associated with theimplant circuit, and during the second power mode, a second power modepulse length of the alternating current signal may be at least as longas the pulse length required to cause neural modulation through theelectrodes associated with the implant circuit. The first power modepulse length may be less than 500 nanoseconds, and the second power modepulse length may be greater than 50 microseconds. The first power modepulse length may be less than 50 microseconds, and the second power modepulse length may be greater than 50 microseconds. The implant circuitmay be associated with electrodes, and transmitting power may includetransmitting an alternating current signal to the implant circuit forconversion to direct current to be supplied to the electrodes, andduring the first power mode, a first power mode current amplitude of thealternating current signal may be lower than a current amplituderequired to cause neural modulation through the electrodes associatedwith the implant circuit, and during the second power mode, a secondpower ode current amplitude of the alternating current signal may be atleast as great as a current amplitude required to cause neuralmodulation through the electrodes associated with the implant circuit.The total time of power delivery in the first mode may be greater thanabout 90% of the therapy period. The total time of power delivery in thefirst mode may be greater than about 95% of the therapy period.

Additional embodiments of the present disclosure may include thefollowing. A sleep disordered breathing therapy implant unit maycomprise a flexible carrier, at least one pair of modulation electrodeson the flexible carrier, and at least one implantable circuit inelectrical communication with the at least one pair of modulationelectrodes, wherein the at least one pair of modulation electrodes andthe at least one circuit are configured for implantation through dermaon an underside of a subject's chin, and wherein the implantable circuitand the electrodes are configured to cooperate in order to generate anelectric field adapted to cause modulation of at least a portion of thesubject's hypoglossal nerve through application of an electric field toa section of the hypoglossal nerve distal of a terminal bifurcation tolateral and medial branches of the hypoglossal nerve. The at least onepair of modulation electrodes may be configured to cause modulation ofat least a portion of the medial branch of the hypoglossal nerve. The atleast one pair of modulation electrodes may be configured to causemodulation of one or more terminal branches of the medial branch of thehypoglossal nerve.

Other embodiments of the present disclosure will be apparent to thoseskilled in the art from consideration of the specification and practiceof the present disclosure.

While this disclosure provides examples of the neuromodulation devicesemployed for the treatment of certain conditions, usage of the disclosedneuromodulation devices is not limited to the disclosed examples. Thedisclosure of uses of embodiments of the invention for neuromodulationare to be considered exemplary only. In its broadest sense, theinvention may be used in connection with the treatment of anyphysiological condition through neuromodulation. Alternative embodimentswill become apparent to those skilled in the art to which the presentinvention pertains without departing from its spirit and scope.Accordingly, the scope of the present invention is defined by theappended claims rather than the foregoing description.

1-9. (canceled)
 10. A method for treating sleep apnea, the methodcomprising: receiving a modulation signal at an implant unit implantedat an internal location on an underside of a subject's chin; applyingthe modulation signal to at least one pair of electrodes associated withthe implant unit to generate an electric field; and causing modulationof a hypoglossal nerve of the subject in response to the electric fieldgenerated by the at least one pair of electrodes, wherein the modulationof the hypoglossal nerve is confined to a medial branch of thehypoglossal nerve and initiated from a single modulation site along themedial branch.
 11. The method of claim 10, wherein the modulation signalis applied at a location along the hypoglossal nerve distal of aterminal bifurcation of the hypoglossal nerve into lateral and medialbranches.
 12. The method of claim 10, wherein the at least one pair ofelectrodes are configured so as to cause substantially no modulation ofthe lateral branch of the subject's hypoglossal nerve.
 13. The method ofclaim 10, wherein the at least one pair of electrodes are configured forlocation adjacent to a horizontal compartment of a genioglossus muscle.14. The method of claim 10, wherein the at least one pair of electrodescause modulation of terminal fibers of the medial branch of the subjectshypoglossal nerve.
 15. The method of claim 10, further comprisingreceiving the modulation signal via an antenna associated with theimplant unit.
 16. The method of claim 10, further comprising generatingthe modulation signal via at least one processor associated with a powersource.
 17. A method for treating sleep apnea, the method comprising:receiving a modulation signal at an implant unit implanted in a vicinityof a genioglossus muscle of a subject; applying the modulation signal toat least one pair of electrodes associated with the implant unit togenerate an electric field; and causing contractions of the genioglossusmuscle in response to the electric field without causing contractions ofhyoglossus, geniohyoid, or styloglossus muscles of the subject.
 18. Themethod of claim 17, wherein the modulation signal is applied at alocation along a hypoglossal nerve distal of a terminal bifurcation ofthe hypoglossal nerve into lateral and medial branches.
 19. The methodof claim 17, wherein the at least one pair of electrodes are configuredso as to cause contractions of the genioglossus muscle via modulation ofa medial branch of the subject's hypoglossal nerve and to causesubstantially no modulation of the lateral branch of the subject'shypoglossal nerve.
 20. The method of claim 17, wherein the at least onepair of electrodes are configured for location adjacent to a horizontalcompartment of the genioglossus muscle.
 21. The method of claim 17,wherein the at least one pair of electrodes cause the contractions ofthe genioglossus muscle via modulation of terminal fibers of a medialbranch of the subject's hypoglossal nerve.
 22. The method of claim 17,further comprising receiving the modulation signal via an antennaassociated with the implant unit.
 23. The method of claim 17, furthercomprising generating the modulation signal via at least one processorassociated with a power source.
 24. A method for treating sleep apnea,the method comprising: receiving a modulation signal at an implant unitimplanted at an internal location on an underside of a subject's chin;applying the modulation signal to at least one pair of electrodesassociated with the implant unit, wherein the electrodes of the implantunit are located along a medial branch of the subject's hypoglossalnerve proximate to terminal fibers of the medial branch; and causingmodulation of the medial branch of the hypoglossal nerve of the subject,from a single location along the medial branch, in response toapplication of the modulation signal to the at least one pair ofelectrodes.
 25. The method of claim 24, wherein the modulation signal isapplied at a location along the hypoglossal nerve distal of a terminalbifurcation of the hypoglossal nerve into lateral and medial branches.26. The method of claim 24, wherein the at least one pair of electrodesare configured so as to cause substantially no modulation of a lateralbranch of the subject's hypoglossal nerve.
 27. The method of claim 24,wherein the at least one pair of electrodes are configured for locationadjacent to a horizontal compartment of a genioglossus muscle.
 28. Themethod of claim 24, further comprising receiving the modulation signalvia an antenna associated with the implant unit.
 29. The method of claim24, further comprising generating the modulation signal via at least oneprocessor associated with a power source.
 30. The method of claim 24,further comprising causing contractions of a genioglossus muscle of thesubject in response to the modulation of the medial branch.